GIFT   OF 

,  PROF.  W.B.  RISING 


AN    INTRODUCTION 


TO 


QUALITATIVE 

CHEMICAL    ANALYSIS 

BY 

THE   INDUCTIVE  METHOD, 
orf     LABORATORY    MANUAL 

FOR 

COLLEGES  AND  HIGH  SCHOOLS. 


DELOS  FALL,  M.S., 

/  > 

PROFESSOR  OF  CHEMISTRY,  ALBION  COLLEGE. 


LEACH,    SHEWELL,    &   SANBORN, 

BOSTON  AND  NEW  YORK. 


F3 


COPYRIGHT,    1891  -1892, 
BY    DELOS    FALL. 

All  Rights  Reserved. 


C.  J.   PETERS  &  SON, 
TYPOGRAPHERS  AND  ELECTROTYPERS. 


PRESS  OF  BERWICK  &  SMITH. 


PREFATORY   NOTE. 


THIS  manual  is  designed  to  impart  but  little  chemical  truth  directly.  It  aims 
rather  to  lead  the  student  to  gain  that  truth  himself  as  nearly  as  possible  at  first 
hand  and  as  a  product  of  his  own  thinking.  This  he  is  enabled  to  do,  without  waste 
of  time,  guided  as  he  is  by  the  suggestions  of  the  book  and  the  constant  prevision 
of  the  live  teacher. 

The  student  is  first  thoroughly  grounded  in  the  fundamental  ideas  of  chemistry 
before  he  goes  on  to  use  those  ideas  as  tools  in  the  practical  work  of  qualitative 
analysis.  If  he  gains  a  proper  conception  of  the  relation  of  the  atom  to  the  mole- 
cule, of  valence  ;  if  he  masters  the  principles  of  nomenclature  and  the  chemical  equa- 
tion as  set  forth  in  chapters  ii.  and  iii.,  he  will  certainly  acquire  his  chemistry  with 
facility  and  clearness.  That  it  produces  strong,  accurate,  enthusiastic,  and  independ- 
ent students  the  author  has  demonstrated  in  his  own  classes  through  several  years. 

For  the  sake  of  emphasizing  what  is  expressed  elsewhere,  the  author  would  insist 
upon  regular  recitations,  at  stated  times,  upon  the  laboratory  work,  in  which  there 
shall  be  full  and, searching  discussion  of  the  results  obtained,  of  errors  committed, 
how  these  errors  have  arisen  and  how  controlled.  Comparison  of  results  obtained 
and  informal  discussion  of  the  difficulties  to  be  met  with  beget  an  interest  and  en- 
thusiasm for  the  work  which  is  invaluable.  Moreover,  a  few  experiments  fully 
reported  and  discussed  are  of  much  greater  value  than  many  experiments  with 
little  time  given  to  suchdiscussipn. 

ALBION  COLLEGE, 

September,  1892. 


237538 


TABLE    OF    CONTENTS. 


Preface. 

Methods          ....  i 

The  Plan 2 

Time  required          ......                  •                           •  3 

The  Daily  Program 3 

The  Student  in  the  Laboratory         .                                                                  •  4 

CHAPTER   I.  — Preliminary  Definitions 7 

Analysis,   Synthesis,  Atom,  Molecule,  Element,    Compound,   Mix- 
ture, Chemical   Affinity,  Chemical  Action,   Chemical   Compounds, 
Valency,  Atomic  Weight,    Molecular  Weight,    Metal,  Non-metal, 

Satisfied  and  Unsatisfied  Compounds,  Chemical  Symbols          .         .  8 

Table  of  Elements         .........  9 

Chemical  Formulas,  Oxides,  Hydroxides,  Acids,  Salts      .         .         .11 

CHAPTER   II.— Nomenclature        .                 12 

List  of  Acids  and  Formulas      .         .         .         .         .         .         .         .12 

Nomenclature  of  Acids :    Oxacids,   Hydracids,  Exchangeable    Hy- 
drogen, Acid  Radical,  Bibasic  and  Tribasic  Acids    .         .         .         .12 

Nomenclature  of  Salts 13 

Neutralization  ............  13 

Naming  Salts,  Writing  Formulas 14 

CHAPTER   III.  — The  Laboratory 16 

Chemicals    and    Apparatus,   Inventory  of  Chemicals    on    Student's 

Table    ....        ...  •    \: 17 

Inventory  of  General  Table     v 17 

Apparatus  for  Student's  Table 19 

CHAPTER  IV.  — Solids  and  Liquids 22 

To  Change  Solids  into  Liquids 22 

To  Change  Liquids  into  Solids 24 


VI  CONTENTS. 


PAC.K 


CHAPTER   V.  — Chemical  Equations       .  ...        26 

Method  of  Writing,  Method  of  discussing        ....        26-29 

Practical  Suggestions    ........  30 

Table  of  Solubilities  .  .  .  .  .  .  .  .  .31 

CHAPTER  VI .  —  Grouping  of  the  Metals  .  .  32 

First  Group  of  Metals  .  . 32 

Second  Group  of  Metals       .  .         .         .         .         .         .         3-- 

Third  Group  of  Metals  .  .  .  .  .  .  .  .  -34 

Fourth  Group  of  Metals 35 

Fifth  Group  of  Metals  .  .  . 35 

Table  of  Grouping  of  Metals  .....  .  .  .  .  37 

CHAPTER  VII.  -  Separation  of  the  Metals  of  First  Group  .  .  38 

Method  of  Separation 38 

Confirmatory  Tests  ...  .  . 39 

Synoptical  View 40 

CHAPTER   VIII.  —  Occurrence  in  Nature  of  First  Group  Metals        .    41 

CHAPTER   IX.  — Separation  of  Metals  of  Second  Group        .        .  43 

Method  of  Separation,  Marsh's  Test,  Spot  Tests      .         .         .  43-45 

Specimen  Pages  from  Student's  Note  Book 45 

Confirmatory  Tests  .         .         .         ....         .         .         .  -47 

Synoptical  View 48 

CHAPTER  X.  — Occurrence  in  Nature  of  Second  Group  Metals        .    49 

CHAPTER   XI,  —  Separation  of  Metals  of  Third  Group  .        .        51 

Table  Work      .         . '.  .              5I 

Questions  on  the  Table  Work             •'.,.-        .         .         .  .         .         51 

A  Study  in  Oxidation       .        ..    •      . 52 

Tests  for  Fe,  Cr,  and  Al  " ,  .         .         .         .         .         .  ;         .         53 

Tests  for  Mn,  Zn,  Co,  Ni          .         .         .         .         .         .  .         .54 

Confirmatory  Tests                 .         .         ...         .  .         .         54 

Synoptical  View        .                  .         .         ..        .         .         .  .         -56 

CHAPTER  XII.  — Occurrence  in  Nature  and  Uses  of  Third  Group 
Metals  57 

CHAPTER   XIII.  —  Separation  of  Metals  of  Fourth  Group        .        .  59 

Table  Work,  Questions  on 59 

Confirmatory  Tests  . 61 

Synoptical  View  .         .         .         .         ..      ."      .        ..         .  62 

CHAPTER  XIV.  —  Occurrence  and  Uses  of  Fourth  Group  Metals  .  63 
CHAPTER  XV.  —  Separation  of  Metals  of  the  Fifth  Group  .  .  65 
CHAPTER  XVI.  —  Occurrence  and  Uses  of  Fifth  Group  Metals  .  67 


CONTENTS.  Vii 

CHAPTER  XVII.  —  The  Periodic  Law  of  the  Elements  ...        69 
CHAPTER  XVIII.  —  Unknowns,  Mixtures         .        .        .        .71,72 

CHAPTER  XIX.— Acids 74 

Classification  of  Acids      .........  74 

Notes  and  Queries         .........  75 

Examination  of  Salts  for  Acids 75 

Confirmatory  Tests 76 

CHAPTER  XX. —Some  Dry  Processes       .        .  .82 

Flame  Tests,  on  Charcoal,  Borax  Bead 82,  83 

Care  of  Platinum  vessels 83 


PLANS   AND   METHODS   OUTLINED. 


LABORATORY  practice,  as  often  carried  on,  consists  in  setting 
before  the  student  a  task  to  perform,  the  end  of  which  is  known 
to  him  as  well  at  the  beginning  of  a  series  of  experiments  as  at 
its  close.  He  may  see  the  fact  more  clearly,  but  the  substance  of 
the  truth  he  knew  to  begin  with.  Recognizing  this,  he  assumes 
at  least  an  attitude  of  doubt  as  .to  the  value  of  laboratory  work. 
Especially  is  this  true  when  he  comes  fresh  from  the  study  of 
history  or  language,  where  he  has  been  trained  to  regard  the 
printed  page  as  the  only  authority  obtainable  or  necessary. 

The  object  sought  in  conducting  the  student  through  a 
course  in  qualitative  chemistry  by  the  method  embodied  in  this 
book,  is  to  counteract  this  tendency  to  undervalue  laboratory 
work,  and  also  to  place  him  as  nearly  as  possible,  from  the  first, 
under  the  conditions  enjoyed  by  the  original  investigator. 

For  example,  a  frequent  method  of  procedure  is  to  make  the 
statement  to  the  student  that  the  reagent  hydrochloric  acid 
will  only  precipitate  silver,  lead,  and  mercurous  salts.  He 
seldom  doubts  this,  and,  acting  on  his  previously  acquired  habit 
of  regarding  the  printed  statement  as  sufficient  authority,  he 
does  not  appreciate  the  desirability  or  necessity  of  demonstrat- 
ing it.  If  he  does  proceed  to  investigate  the  question  by 
practical  tests,  his  work  will,  in  many  cases,  consist  in  making 
the  three  precipitates  in  question,  and  perhaps  trying  the  effect 
of  the  reagent  on  one  or  two  additional  salts.  It  will  be  seen 
that  this  is  no  demonstration  whatever. 

If,  however,  he  should  be  sent  to  the  laboratory  with  the 


2  PLANS    AND    METHODS    OUTLINED. 

single  question,  "  How  does  hydrochloric  acid  affect  salts  in 
solution  when  added  to  them  ?  "  it  is  clear  he  could  not  con- 
sider his  work  as  completed  until  he  had  applied  the  acid  to 
representative  salts  of  at  least  all  the  more  commonly  occurring 
metals.  When  this  was  done,  he  would  discover  the  fact  that 
hydrochloric  acid  will  precipitate  silver,  lead,  and  mercurous 
salts,  and  no  otJier.  An  easy  deduction  from  this  work  leads 
him  to  the  capital  truth  that  the  reagent  hydrochloric  acid  will 
separate  salts  of  these  metals  from  all  others.  He  would 
then  feel  himself  to  be,  and  would  be,  quite  as  much  the  dis- 
coverer of  the  truth  as  the  one  who  first  came  into  possession 
of  it. 

It  will  be  objected  that  it  is  wrong  to  oblige  the  student  to 
pursue  this  work  of  discovering  truths  already  well  established  ; 
that  he  ought  to  enter  into  and  take  advantage  of  the  fruits  of 
previous  toilers,  and  himself  push  out  into  fields  not  yet  occu- 
pied. This  is  very  true,  but  a  great  defect  in  the  student's 
training  will  arise  from  the  fact  that  his  habits,  his  methods  of 
study  and  investigation,  are  given  him  by  his  first  lessons.  If 
his  initial  lessons  do  not  introduce  him  to  the  true  scientific 
method  it  is  doubtful  whether  he  will  appreciate  it  fully  when 
set  before  him  farther  on  in  his  course. 

It  will  also  be  objected  that  this  course  will  take  more  time 
than  can  ordinarily  be  given  to  this  subject.  In  answer  to  this 
it  may  be  urged  that  the  teacher  must  not  regard  time  when  it 
weighs  against  false  or  true  methods  ;  that  slowness  at  the 
start  only  makes  progress  more  rapid  when  correct  habits  have 
been  formed.  This  the  writer  has  found  to  be  true  in  his  trial 
of  this  method  through  several  years. 

The  Plan. — The  plan  may  be  described  as  a  combination  of 
(i)  original  investigation  and  (2)  references  to  authorities. 

In  the  beginning  (i)  will  be  a  very  small  factor  and  (2)  cor- 
respondingly large.  As  experience  in  manipulation,  observa- 
tion, and  interpretation  increases,  (i)  will  increase  and  the 
necessary  dependence  on  (2)  will  decrease.  To  the  experi- 


PLANS    AND    METHODS    OUTLINED.  3 

enced  chemist  (i)  is  very  large  and  (2)  very  small ;  in  other 
words,  he  is  his  own  authority. 

Time  Required.  —  Two  terms  of  fourteen  weeks  each  are 
thought  to  be  sufficient  to  cover  a  course  in  general  descriptive 
chemistry,  and  also  lay  a  thorough  foundation  for  a  course  in 
qualitative  analysis.  The  non-metals  may  be  studied  from 
some  general  text-book,  this  occupying  three  or  four  fifths  of 
the  first  term.  The  qualitative  work  may  begin  after  the 
middle  of  the  term,  with  one  or  two  recitations  per  week,  or 
this  work  may  be  deferred  till  the  beginning  of  the  second 
term.  After  the  metals  of  a  given  group  have  been  studied, 
the  general  text-book  may  again  be  used  for  answers  to  the 
questions  under  "  Occurrence  in  Nature." 

The  Daily  Program,  —  The  advance  work  for  each  day  will 
consist  in  finding,  by  actual  tests  in  the  laboratory,  or  by 
reference  to  proper  authority,  answers  to  the  questions,  making 
proper  memoranda  of  all  transactions,  and  writing  equations 
for  all  cases  of  chemical  action. 

The  class  will  then  come  together  to  make  report  of  progress 
and  for  a  mutual  discussion  by  teacher  and  class  of  the  details 
of  the  work,  and  especially  of  all  deductions  and  truths  which 
have  been  brought  to  light.  Much  time  should  be  spent  in  the 
recitation  room,  tabulating  and  comparing  results,  discussing 
the  work,  and  formulating  principles. 

While  this  discussion  is  in  progress,  the  student  should  write 
out  in  full,  by  direct  discourse,  so  much  of  the  theory  and 
practice  of  chemical  analysis  as  his  work  has  made  clear  to 
him. 

The  catechetical  method  is  only  employed  where  it  is 
thought  to  be  the  clearest  method  to  lead  the  learner  to  the 
truth  ;  nor  is  it  claimed  that  all  the  queries  that  ought  to  be 
started  are  here  given.  These  are  merely  typical  of  many 
others  that  will  spring  up  in  the  mind  of  the  thoughtful  stu- 
dent. That  which  is  presented  here  is  only  the  skeleton  or 
framework  ;  the  body  of  truth  must  be  built  up  by  the  united 


4  PLANS    AND    METHODS    OUTLINED. 

efforts  of  the  live  and  energetic  teacher  and  the  enthusiastic 
student.  Indeed,  it  must  be  insisted  that  this  book  is  not  at 
all  complete  in  itself  ;  that  the  one  claim  it  puts  forward  for 
originality  lies  in  the  fact  that  it  continually  compels  the 
student  to  seek,  by  tests  in  the  laboratory  or  in  other  books, 
the  information  he  desires. 

To  the  Student. 

On  entering  a  laboratory,  whether  physical,  biological,  or 
chemical,  the  student  should  thoroughly  appreciate  the  changed 
relations  and  different  surroundings  in  which  he  finds  himself. 
He  has  studied  literature,  history,  mathematics,  language,  or 
philosophy,  in  the  privacy  and  quiet  of  his  own  room  ;  he  has 
studied  from  books,  but,  on  taking  up  the  study  of  the  natural 
sciences,  his  books  have  been  taken  from  him,  and  in  their 
place  he  is  given  specimens  and  objects  of  natural  history.  He 
is  led  to  look  at  these  objects,  observe  as  many  characteristics 
as  possible,  make  notes,  arrange  and  classify  the  facts  and  truths 
thus  obtained,  draw  his  own  conclusions,  and  discover  underly- 
ing principles  and  laws. 

Every  true  student  will  delight  in  discovering  truth  for  him- 
self, and  in  order  to  accomplish  this  he  must  early  be  taught 
the  methods  by  which  this  appeal  to  first  sources  is  made.  No 
field  presents  better  opportunities  for  this  kind  of  study  than 
chemistry. 

.  Many  difficulties  lie  in  the  way  of  such  methods,  and  it  is  the 
student's  first  business  to  know  what  those  difficulties  are  and 
conquer  them  as  soon  as  possible. 

(1)  He  studies  in  the  laboratory  in  company  with  other  mem- 
bers of  his  class,  and  this  necessitates  some  confusion   which 
distracts  his  attention  from  the  work  in  hand.     To  learn  to  iso- 
late himself  from  all  others  by  becoming  absorbed  in  his  work 
is  his  first  duty. 

(2)  His  apparent  progress  at  first  will  necessarily  be  some- 
what slow.     He  must  learn  to  appreciate  the  greater  value  of  a 


PLANS    AND    METHODS    OUTLINED.  5 

single  truth  acquired  by  himself  than  many  learned  at  second- 
hand. 

(3)  The  student  naturally  expects  by  this  method  to  obtain 
only  those  facts  which  are  made  apparent  to  him  through  his 
physical  senses.     One  of  the  early  things  which  he  must  learn 
is  that  in  the  acquisition  of  truth  he  must  enlist  his  whole  being, 
sight,  hearing,  touch,  etc.  ;  in  a  still  greater  degree  there  must 
be  brought  into  action  his  reason,  judgment,  and  imagination. 
All  the  powers  of  the  mind  and  body  must  be  so  disciplined 
and  trained  that  they  can  be  concentrated  upon  the  particular 
object  of  study. 

(4)  His  memory  must  grasp  and  hold  the  whole  of  a  series 
of   facts    until    they    can    be    brought    into    their   proper  rela- 
tions and  the  principles  and  laws  discovered  which  bind  them 
together. 

(5)  He  must  be  a  diligent  student  of  language  in  order  that 
what  he  sees  may  be  clearly  described.     Knowledge  is  of  little 
value  if  for  lack  of  power  of  expression  it  must  forever  be  locked 
up  in  the  mind  of  the  one  who  discovered  it. 

(6)  He  must  early  learn  that  courage  and  persistence  are 
needed  if  he  would  come  into  a  clear  apprehension  of  truth. 
He  must  be  willing  to  do  much  of  what  has  been  denominated 
"  dead  work  ; "  that  is,  work  that  has  been  done  by  others  before 
him.     Much  of  his  work  he  must  do  over  and  over  again,  until, 
by  familiarity  with  it,  its  true  significance  is  brought  to  light. 

This  leads  to  the  consideration  of  another  question  ;  namely, 
Where  shall  a  student's  work  stop  ?  It  may  stop  at  any  one  of 
several  points,  each  denoting  varying  degrees  of  excellence  in 
that  work.  For  example,  he  may 

(1)  Be   content    to   read   a  statement    and    simply  give    his 
assent  to  it. 

(2)  He  may  so  memorize  that  statement  as  to  be  able   to 
reproduce  it  when  necessity  requires. 

(3)  He  may  verify  the  truth  by  the  observation  and  study  of 
an  appropriate  experiment  in  the  laboratory. 


6  PLANS    AND    METHODS    OUTLINED. 

(4)  To  obtain  a  still  more  definite  knowledge  of  the  point  in 
hand  he  may  prepare  abstracts,  and  illustrate  by  diagrams. 

(5)  He  may  obtain  by  any  of  these  partial  methods  a  con- 
ception of  the  truth,  by  which  he  is  enabled  to  make  a  creditable 
recitation,  provided  he  has  help  from  his  teacher,  and  the  privi- 
lege of  retracing  his   steps   and   thus  amending  his  previous 
statement  ;  or, 

(6)  He  may  impose  upon  himself  the  highest  and  best  test 
of  the  accuracy  of  the  knowledge   he   has   obtained,  and  his 
familiarity  with  it,  by  reducing  that  knowledge  to  a  clear,  con- 
cise, and  original  written  statement  which  will  withstand  the 
criticism  of  others. 

Some  students,  so-called,  are  content  to  stop  at  the  first-men- 
tioned point ;  most  students  go  as  far  as  the  second  or  third  ; 
many  faithfully  practice  the  fourth,  and  strive  to  attain  to  the 
degree  of  excellence  suggested  by  the  fifth  point.  A  notable 
and  praiseworthy  few  are  not  satisfied  with  anything  less  than 
the  accomplishment  of  the  work  contemplated  in  the  sixth  sug- 
gestion. 

The  author  records  it  as  his  deliberate  judgment,  after  years 
of  experience,  that  in  order  that  the  greatest  good  shall  be  de- 
rived from  the  work  which  follows,  the  student  must  prepare  a 
note-book  covering  the  entire  work.  It  may  simply  be  supple- 
mental to  this  book  ;  but  a  much  better  plan  is  to  make  it 
complete  in  itself,  including  title-page,  a  short  introduction, 
preliminary  definitions,  laboratory  memoranda,  equations,  tabu- 
lated work,  synopses,  and  especially  all  facts  and  principles 
which  have  been  deduced  from  the  work.  Nothing  else  can 
take  the  place  of  this  part  of  the  study. 


QUALITATIVE  CHEMICAL  ANALYSIS. 


CHAPTER    I. 
PRELIMINARY  DEFINITIONS. 

What  is  analysis  ?     Synthesis  ? 

What  is  chemical  analysis  ? 

What  is  organic  analysis  ?     Inorganic  analysis  ? 

What  is  qualitative  analysis  ?     Quantitative  analysis  ? 

What  is  volumetric  analysis  ?     Gravimetric  analysis  ?     - 

There  are  certain  fundamental  ideas  and  principles  concern- 
ing the  atom  and  molecule,  and  their  relations  to  each  other, 
which  can  not  well  be  illustrated  by  simple  experiments,  and 
much  less  can  they  be  demonstrated  by  this  method.  It  is, 
however,  very  necessary  to  have  them  in  mind  as  the  work  con- 
templated in  the  following  pages  is  entered  upon.  These  have 
largely  been  met  and  studied  in  the  general  chemistry  which 
the  student  is  supposed  to  have  had  preparatory  to  this  course, 
and  they  are  repeated  here  by  way  of  review. 

Answers  to  the  following  questions  may  be  supplied  by  the 
teacher,  or  sought  out  in  any  reliable  text-book  on  general 
chemistry. 

What  is  an  atom  ?  A  molecule  ?  A  simple  molecule  ?  A 
compound  molecule  ? 

What  are  elements  ?     Compounds  ?     Mixtures  ? 


8  QUALITATIVE    ANALYSIS. 

Perform  the  following  experiments,  and  find  illustrations  of 
the  above  three  terms. 

1.  Add  carbon  disulphide  separately  to  some  flowers  of  sul- 
phur and  iron  powder  and  note  the  effects. 

2.  Try  the  effect  of  a  magnet  on  each. 

3.  Thoroughly  mix,  with  a  pestle  and  mortar,  seven  parts  by 
weight  of  the  iron  and  four  parts  of  the  sulphur. 

4.  Repeat    experiments    I   and   2  on    the    substance   in    the 
mortar. 

5.  Fill  a  dry  test-tube  one-third  full  with  the  substance  from 
the  mortar,  and  strongly  heat  the  lower  end. 

6.  After  fusion  has  taken  place,  and  the  substance  has  cooled, 
repeat  experiments  I  and  2. 

Define  chemical  affinity  ;  chemical  action  ;  chemical  work. 

Atoms  when  apart  possess  chemical  affinity  or  chemical 
energy.  This  energy  may  be  thought  of  as  the  variety  called 
potential ;  when  this  is  transformed  into  kinetic  energy,  or 
energy  of  motion,  chemical  act/on  takes  place  ;  the  work  done 
or  result  produced  is  a  chemical  compound. 

What  is  understood  by  atomic  weight  ?  By  molecular- 
weight  ? 

What  is  a  metal  ?     A  non-metal  ? 

In  the  decomposition  of  compounds  by  the  electric  current 
it  is  found  that  invariably  hydrogen  and  the  metals  seek  the 
negative  pole  of  the  battery,  while  the  non-metals  are  found  at 
the  positive  pole.  In  this  electrical  behavior  of  the  chemical 
elements  there  is  a  possible  explanation,  by  analogy  at  least,  of 
the  fact  that  the  strongest  chemical  affinity  exists  when  a 
metal  is  brought  near  to  a  non-metal,  the  latter  elements  hav- 
ing only  a  secondary  attraction  for  each  other,  and  the  metals 
scarcely  ever  uniting  together.  In  the  great  majority  of  cases, 
therefore,  chemical  compounds  contain  both  metals  and  non- 
metals. 


TABLE    OF   ELEMENTS. 


TABLE  OF  70  ELEMENTS. 

This  table  represents  trustworthy  results,  reduced  to  a  uniform  basis  of  comparison,  with 
Oxygen  =  16  as  a  starting-point  of  the  system.  No  decimal  places  representing  large  uncer- 
tainties are  used.  When  values  vary,  with  equal  probability  on  both  sides,  so  far  as  our  present 
knowledge  goes,  as  in  the  case  of  cadmium  (111.8  and  112.2),  the  mean  value  is  given 
in  the  table. 


! 

NAME. 

SYMBOL. 

ATOMIC  WEIGHT. 

VALENCE. 

NAME. 

SYMBOL. 

ATOMIC  WEIGHT. 

VALENCE. 

Aluminum  ... 
Antimony  

Al 
Sb 
As 
Ba 
Bi 
B 
Br 
Cd 
Cs 
Ca 
C 
Ce 
CI 
Cr 
Co 
Cb 
Cu 
Er 
F 
Ga 
Ge 
Gl 
Au 
H 
In 
I 
Ir 
Fe 
La 
Pb 
Li 
Mg 
Mn 

^ 

27. 

120. 

75- 
137- 
208.9 
n. 
79-95 

112. 
132.9 
40. 
12. 
I4O.2 

35-45 
52.1 

59- 
94. 

6.V4 
166.3 

59- 
69. 

72-3 
9- 
197-3 
1.007 

:% 
T 

138.2 
206.95 
7.02 
24-3 

55- 

200. 
96. 

II,  III 
III,  V. 
Ill,  IV. 
II. 
Ill,  V. 
Ill   . 
I.  (V). 

II. 
II. 

(II),  IV. 
I,  V. 

(II),  III. 

II,  IV. 

I,  II. 

I,   (V). 

III. 
I. 

I,  (V). 

II,  III. 

II,  IV. 

II. 

II,  IV,  VI. 

I,  II. 

Neodymium3.. 
Nickel  

Nd 
Ni 
N 
Os 
0 
Pd 
P 
Pt 
K 
Pr 
Rh 
Rb 
Ru 
Sm 
Sc 
Se 
Si 
Ag 
Na 
Sr 
S 
Ta 
Te 
Tb 
Tl 
Th 
Sn 
Ti 
W 
U 
V 
Yb 
Yt 
Zn 
Zr 

HO.S 
58.7 
14.03 
I9I.7 

1  6. 
106.6 
3i- 
195- 
39-  II 
143-5 
103-5 
85-5 
101.6 
150. 
44- 
79- 
28.4 
107.92 

li 

32.06 
182.6 
"S- 
159-5 
204.18 
232.6 
119. 
48. 
184. 
239.6 
Si-4 
173- 
89.1 
65-3 
90.6 

II,  IV. 
(l),  III.  IV. 

II. 

(l),  III,  V. 

("),  iv. 
I. 

II. 

IV. 

I. 

II. 

II,  IV,  (Vl). 
II,  IV. 

II. 

Bismuth  

Palladium  
Phosphorus  .  .  . 

Bromine  
Cadmium  .... 

Potassium  .... 
Praseodymium3 

Calcium  , 

Rubidium  
Ruthenium  ... 
Samarium  
Scandium  
Selenium  

Chlorine  
Chromium  .  .. 
CobaJt  

Columbium1). 

Erbium  
Fluorine  
Gallium  
Germanium  .  . 
Glucinum3)  . 
Gold  

Silver 

Strontium  
Sulphur  

Tantalum  
Tellurium  
Terbium  
Thallium  
Thorium  
Tin      

Hydrogen  .  .  . 
Indium  

Iridium  

Titanium  
Tungsten  
Uranium  
Vanadium  
Ytterbium  

Lanthanum  .  . 
Lead 

Lithium  
Magnesium  .  . 
Manganese  .. 
Mercury  
Molybdenum. 

Zinc          

Zirconium  .... 

1)  Or  Niobium. 

2)  Or  Beryllium. 


3)  Didymium  now  split  into  Neo-  and  Praseo-Didymium. 

4)  Standard,  or  basis  of  the  system. 


IO  QUALITATIVE    ANALYSIS. 

What  is  a  saturated  compound  ?  An  unsaturated  com- 
pound ? 

What  kind  of  compounds  are  capable  of  entering  into 
chemical  action  without  being  first  decomposed  ? 

NOTE.  —  The  theories  involved  in  the  foregoing  questions  are  very  complex,  and  it  is  not  expected 
that  they  will  be  perfectly  clear  to  the  mind  of  the  beginner;  but  their  constant  use  and  universal 
application  to  all  chemical  problems  will  gradually  bring  their  deep  significance  into  view. 

What  are  chemical  symbols  ? 

What  are  chemical  formulas  ?     Give  illustrations. 

NOTE.  —  The  Quantitative  Chemist  first  learns  what  the  chemical  formula  of  a  certain  substance  is, 
and  the  Qualitative  Chemist  accepts  his  authority  and  follows  it. 

What  is  meant  by  valence  ? 

What  is  a  univalent  element  ?  A  bivalent  element  ?  A 
trivalent  element  ?  A  quadrivalent  element  ? 

What  is  a  monad  ?     A  diad  ?     A  triad  ?     A  tetrad  ? 

When  is  an  element  said  to  have  "  one  bond  "?  "  Two 
bonds  "  ?  "  Three  bonds  "  ?  etc. 

How  may  the  valence  of  an  element  oftentimes  be  ob- 
served from  a  formula? 

What  is  the  valence  of  Cl  in  HC1  ?  Sb  in  SbCl3  ?  Mg  in 
MgSO4  ?  Fe  in  Fe2  (SO4)3  ?  SO4  in  H2SO4  ?  K  in  KC1  ? 
P04  in  K3P04  ?  O  in  H2O  ?  C  in  CO2  ? 

What  is  the  water  of  crystallization  ?  When  should  this 
be  taken  into  account  and  included  in  the  formula  ? 

Take  a  piece  of  glass  tubing  20  cm.  long;  soften  the  middle  point  in 
the  flame,  and  draw  the  two  halves  apart,  thus  making  two  tubes  closed  at 
one  end.  Place  a  small  piece  of  the  mineral  gypsum  in  the  bottom  of  one 
of  these  tubes  and  heat.  Drops  of  water  will  be  seen  to  condense  in  the 
upper  part  of  the  tube. 

Heat  a  weighed  amount  of  gypsum  in  a  porcelain  crucible,  and  from 
the  weight  of  the  residue  determine  what  per  cent  of  water  gypsum  contains. 
Repeat  the  experiment  with  sal  soda. 


PRELIMINARY    DEFINITIONS.  II 

What  are  deliquescent  compounds  ?  Efflorescent  com- 
pounds ?  Expose  a  piece  of  solid  potassium  hydroxide  to  the 
air.  Do  the  same  with  some  crystals  of  sodium  sulphate. 

What  are  oxides  ?     Give  examples. 

What  are  hydroxides  ?     Give  examples. 

What  are  acids  ?     Give  examples.     (Study  litmus.) 

What  are  salts  ?     Give  examples. 

NOTE.  — The  last  four  questions  indicate  a  classification  to  which  nearly  all  chemical  compounds 
may  be  referred. 

What  is  a  normal  salt  ?  An  acid  salt  ?  A  basic  salt  ?  A 
double  salt  ? 


CHAPTER    II. 

NOMENCLATURE. 

List  of  Acids  and  Formulas, 

Hydrochloric  acid  ...  .  HC1 ;  Chloric  acid  .  .  .  .  HC103 
Hydrobromic  acid  ....  HBr ;  Bromic  acid  .  ...  .  .  HBr03 

Hydriodic  acid     .      .      .      ...    HI ;     lodic  acid HI03 

Hydrosulphuric  acid      .      .      .     H2S ;     Sulphuric  acid      ....   H0S04 
Hydroferrocyanic  acid     ....     H^eC^N,, ; 
Hydroferricyanic  acid    ....        H3FeC6N6 ; 

Nitrous  acid HN02 ;     Nitric  acid HN03 

Acetic  acid  .....  HC2H302 ;  Oxalic  acid  .."...  H0C.,04 
Carbonic  acid  .  .  .  .  .  H2C03 ;  Phosphoric  acid  .  .  .  H3P04 
Arsenious  acid  ....  H3As03  ;  Arsenic  acid  ....  H3As04 
Tartaric  acid  ....  H2C4H406  ; 

NOTE.  —  Very  much  depends  upon  a  thorough  and  familiar  acquaintance  with  the  foregoing  list  of 
acids  and  their  formulas. 

From  the  preceding  list  it  will  be  noticed  that  acids  may 
be  divided  into  two  classes,  (i)  those  containing  oxygen  and 
(2)  those  which  do  not  contain  that  element.  The  former  are 
called  oxacids,  the  latter  hydracids.  And  again,  of  two  oxacids 
differing  in  the  amount  of  the  oxygen,  that  one  having  the 
greater  amount  is  given  a  name  terminating  in  ic,  the  other  in 
ous.  Classify  the  above  list. 

That  portion  of  the  hydrogen  of  the  acid  which  is  capable 
of  being  displaced  by  a  metal  in  the  formation  of  a  salt  is 
spoken  of  as  the  exchangeable  hydrogen,  the  remainder  of  the 
acid  as  the  acid  radical.  Illustrate. 

The  exchangeable  hydrogen  may  not  be  all  of  that  ele- 
ment contained  in  the  acid.  For  example,  acetic  acid  contains 
four  atoms  of  hydrogen,  and  only  one  of  them  capable  of  being 
displaced  by  the  metal. 

12 


NOMENCLATURE.  13 

What  are  bi-basic  and  tri-basic  acids  ?     Find  illustrations 
in  the  above  list. 

Nomenclature  of  Salts. 

The  laws  governing  the  nomenclature  of  salts  are  very 
simple,  and  have  universal  application. 

(1)  If  the  salt  has  been  formed  from  a  hydracid,  its  name 
terminates  in  ide. 

(2)  An  ic  oxacid  gives  rise  to  salts  which  terminate   in  ate, 
and 

(3)  ous  oxacid s  form  salts  in  He. 

The  laws  which  govern  the  naming  of  salts  may  be  sum- 
marized as  follows  : 

ic  form  salts  in  ate. 


f  OXACIDS   .  .  . 
ACIDS  J  ^  ous 

L  HYDRACIDS form  salts  in  ide. 

Let  the  student  illustrate  the  above  laws  by  numerous 
examples. 

Having  the  formula  of  an  acid,  how  may  you  give  its 
name  ? 

What  simple  test  is  usually  employed  to  determine  whether 
a  given  substance  is  acid  or  not  ? 

Neutralization. 

Chemical  substances  are  either  acid,  alkaline,  or  neutral  to 

litmus  paper. 

Carefully  neutralize  a  given  measured  quantity  of  dilute 
HC1  with  dilute  NaOH  and  note  the  quantity  of  the  alkali 
necessary  for  the  purpose.  Make  another  test  with  the  same 
substances,  using  different  quantities.  If  great  care  is  taken, 


14  QUALITATIVE    ANALYSIS. 

and  the  exact  point  of  neutralization  ascertained  each  time,  the 
four  amounts  used  will  approximately  form  a  proportion. 

Measure  the  amounts  of  solution  used  in  each  case  by  means  of  a  burette, 
and  ascertain  whether  acid,  alkali,  or  neutral,  with  litmus  paper. 

Considering  the  last  experiment,  is  neutralization  a  phys:- 
cal  or  a  chemical  action  ? 

What  is  formed  when  HC1  is  treated  with  NaOH  ? 

Repeat  the  above  experiment  with  KOH  and  HNO3 ;  with 
NH4OH  and  HC2H3O2 ;  with  NH4OH  and  HC1 ;  with  NaOH 
and  HC1. 


Exercises  in  Naming  Salts  from  their  Formulas. 

Name  the  compound  represented  by  the  formula  K2SO4. 

If   you  cannot    readily    do    so,  determine   what    it    is    by 
answering  the  following  questions  : 

1.  What  metal  does  it  contain  ? 

2.  What  acid  is  represented  in  it  ? 

3.  Is  this  an  oxacid  or  a  hydracid  ? 

4.  If  the  former,  is  it  ic  or  ous  ? 

5.  How  does  the  salt  name  terminate  which  is  formed  from 
this  acid  ? 

Having  answered  these  questions,  we  are  ready  to  affirm 
that  the  given  salt  is  Potassium  Sulphate. 
In  like  manner  name  the  following : 

CaS04,   Ca(N03)2,   KN03,   KC2H302,  NaCl,  FeCl2,  FeCl3, 
SbCl3,    (What  is  the  valency  of  Sb?),   K3P04,   Ca3(P04)2, 
AgCl,  Pb(N03)2,  Bi(N03)3,  NaN03,  CaHP04,  Pb(C2H302)2, 
K3FeC6N6,  K4FeC6N6,  Na3P04,  Na2HP04,  NaH2P04,  K2C204, 

Ca(C18H3502)2     (Stearicacid),  SeCl4,   MgBr2. 


NOMENCLATURE.  15 

Exercises  in  Writing  Formulas. 

Write  the  formula  for  Potassium  Sulphate.  In  order  to 
do  this  intelligently  and  with  confidence,  hold  in  mind  the 
following  points  : 

1.  What  acid  is  suggested  by  the  name  ? 

2.  What  is  the  formula  for  this  acid  ? 

3.  What  is  the  valency  of  the  acid  radical  ? 

4.  What  is  the  symbol  and  valency  of  the  metal  ? 

5.  The  number  of  "  bonds"  of  the  metal  must  equal  those 
of  the  acid  radical  in  every  satisfied  compound. 

The  formula  is  therefore  K2SO4. 

In  a  like  manner  write  the  formulas  for  the  following : 

Sodium  1     (  Chloride 
Potassium  Acetate 

Calcium  |    Sulphate 

Lead  I    j   Sulphide 

Iron  j     j    Nitrate 
Silver  Oxalate 

Bismuth  Phosphate 

Magnesium  J     ^  Ferrocyanide 

The  student  may  practice  writing  formulas  for  salts  formed 
by  each  of  the  following  metals  with  each  of  the  following 
acids : 

Sodium         ^  (  Hydrochloric  Acid 
Magnesium    >  2  Carbonic  Acid 
Bismuth        )  {  Hydrosulphuric  Acid 

Calcium  \  f  Phosphoric  Acid 

Zinc          I  J   Acetic  Acid 

Copper     j  j    Sulphuric  Acid 

Cobalt  I  Nitric  Acid 


CHAPTER   III. 
THE   LABORATORY, 

Make  a  complete  inventory  of  the  chemicals  on  your  table, 
classifying  them  into  salts,  bases,  acids,  etc. 

Make  an  inventory  of  the  apparatus,  using  the  correct 
technical  name  for  each  article. 

Do  the  same  for  the  material  to  be  found  on  the  General 
Table. 

What  condition  are  these  chemicals  in  when  purchased 
for  the  laboratory? 

How  have  they  been  prepared  for  use  ? 

It  is  very  desirable  that  each  student  should  have  a  sep- 
arate laboratory  table,  on  which  may  be  kept  certain  chemical 
reagents  and  apparatus  for  his  personal  use. 

A  convenient  working  laboratory  for  eight  students  may 
be  easily  arranged  as  follows  :  a  strong,  well  built  table,  six- 
teen feet  long  and  four  feet  wide,  extends  from  one  side  into 
the  middle  of  the  room.  Lengthwise,  through  the  middle  of 
the  table,  rises  a  partition,  upon  which  are  the  shelves  for 
holding  the  reagent  bottles.  One  shelf,  one  foot  above  the 
surface  of  the  table  and  four  inches  wide,  is  sufficient  for  each 
table.  Two  wash  bowls  situated  as  indicated  in  the  diagram 
will  serve  for  eight  students. 


1 

1 

n 

! 

\J 

00 

4ft  <a      *! 

1           *     ~ 

4ft  £ 

1 

16 


THE    LABORATORY.  I/ 

A  cask  or  tank  in  the  attic  or  upper  part  of  the  room  may 
be  connected  with  the  rain  pipes  on  the  roof,  or  filled  from  the 
public  water  supply,  and  thus  made  to  supply  water  to  the 
wash  bowls,  while  other  pipes  conduct  away  the  waste  liquids. 

In  case  illuminating  gas  can  be  had,  each  table  should  be 
supplied  with  a  Bunsen  burner.  If  gas  can  not  be  had,  the 
alcohol  lamp  may  be  used,  which  will  give  good  results. 

Cupboards  and  drawers  may  be  constructed  underneath 
the  table,  which  will  be  convenient  for  storing  the  student's 
laboratory  apron  or  any  larger  pieces  of  apparatus. 

The  laboratory  should  be  well  ventilated,  some  arrange- 
ment being  especially  necessary  for  conveying  away  noxious 
gases. 

Besides  these  work  tables  there  should  be  a  "  general 
table,"  so  situated  as  to  be  of  easy  access  by  all  the  students 
of  the  class. 

The  liquid  reagents  should  be  kept  in  glass  stoppered 
bottles,  and  preferably  with  labels  blown  in  the  glass. 

The  names  of  sufficient  reagents  are  given  in  the  follow- 
ing table  fully  to  identify  and  separate  the  twenty-five  more 
commonly  occurring  metals,  and  the  acids  with  which  they  are 
usually  combined. 

The  names  and  formulas  are  given,  with  the  number  of 
parts  by  weight  of  water  required  to  dissolve  one  part  of  the 
substance.  The  first  nineteen  mentioned  may  be  kept  on 
the  student's  table. 

NOTE.  — The  order  of  naming  the  reagents  in  the  following  list  will  indicate  a  convenient  arrange- 
ment for  the  laboratory  tables. 

NAMES.  FORMULAS.  PARTS  OF  H20. 

Hydrochloric  Acid,  HC1,  24  per  cent  acid. 

Nitric  Acid,  HN03,  32  per  cent  acid. 

Sulphuric  Acid,  H2S04,  Concentrated. 

Acetic  Acid,  HC2H302,  30  per  cent  acid. 

Hydrosulphuric  Acid,  H2S,  Saturated  solution. 

Ammonium  Hydroxide,  NH4OH,  10  per  cent  of  gal). 


i8 


QUALITATIVE    ANALYSIS. 


NAMES.  FORMULAS.  PARTS  OF  HQ0. 

Ammonium  Chloride, 
Carbonate, 
Sulphide, 
Oxalate, 

Potassium  Bichromate, 
Sulphate, 
Ferricyanide, 
Hydroxide, 

Calcium  Sulphate, 
Chloride, 

Barium  Chloride, 

Silver  Nitrate, 

Lead  Acetate, 

Mercurous  Nitrate, 

Mercuric  Chloride, 

Arsenic  Chloride, 

Antimony  Chloride, 

Stannous  Chloride, 

Bismuth  Nitrate, 

Copper  Sulphate, 

Cadmium  Chloride, 

Ferrous  Sulphate, 

Ferric  Chloride, 

Aluminum  Sulphate, 

Chromium  Sulphate, 

Cobalt  Nitrate, 

Nickel  Nitrate, 

Manganese  Chloride, 

Zinc  Sulphate, 

Barium  Chloride, 

Strontium  Chloride, 

Magnesium  Sulphate, 

Potassium  Iodide, 

Potassium  Sulphocyanide, 

Sodium  Chloride, 

Sodium  Hydrogen  Phosphate, 

Potassium  Ferrocyanide, 

Alcohol, 

Ammonium  Molybdate, 

Acid  in  4  parts  of  Ammonia,  and  pour  the  solution  into  15  parts  of 
dilute  Nitric  Acid  of  s.g.  i  .20  (equal  parts  Nitric  Acid  and  water) .  Let 
stand  a  day  or  two  and  filter. 


NH4C1, 

i 

8. 

(NH4)2C03, 

i 

4+1  part  NH4OH. 

(NH4)2S, 

N 

H4OH  Saturated  with  H2S. 

(NH4)2C204, 

i 

24. 

K2Cr207, 

i 

10. 

K2S04, 

I 

12. 

K3FeC6N6, 

i 

12. 

KOH, 

i 

8. 

CaS04, 

S 

aturated  solution. 

CaCl2, 

i 

8. 

BaCl2, 

I 

10. 

AgN03, 

i 

20. 

Pb(C2H302)2, 

i 

10. 

Hg2(N03)2, 

i 

2o+HN03. 

HgCl2, 

i 

16. 

AsCl3, 

A 

s203+HCl. 

SbCl3, 

i 

10  Acidulated  with  HC1. 

SnCl2, 

i 

10  Acidulated  with  HC1. 

Bi(N03)3, 

H 

20+NH03. 

CuS04, 

i 

12. 

CdCl2, 

i 

12. 

FeS04, 

i 

10. 

FeCl3, 

i 

10. 

A12(S04)3, 

i 

10. 

Cr2(S04)3, 

i 

10. 

Co(N03)2, 

i 

10. 

Ni(N03)2, 

i 

10. 

MnCl2, 

i 

10. 

ZnS04, 

i 

10. 

BaCl2, 

i 

10. 

SrCl2, 

i 

10. 

MgS04, 

i 

10. 

KI, 

i 

20. 

KCNS, 

i 

10. 

NaCl, 

i 

10. 

Na2HP04, 

i 

10. 

K4FeC6N6, 

i 

12. 

C2H5OH, 

Proof  Spirit. 

(NH4)2Mo04, 

dissolve  i  part  of  Molybdic 

THE    LABORATORY.  ip 

Dry  Reagents. 

Sodium  Carbonate,  Na2C03,  or  NaHC03 

Sodium  Borate  (Borax),  Na2B407. 

Potassium  Chlorate,  KC103. 

Nitrate,  KN03. 

Ferrous  Sulphide,  FeS. 

Sulphate,  FeS04. 

Metallic  Zinc,  Zn. 

Microcosmic  Salt,  HNaNH4P04 ;    made  by  dissolving   7  part, 

Na0HP04  and  i  part  NH4C1  in  2  parts  of  boiling  water  and  crystal- 
lizing. 

NOTE.  —  Other  salts  of  the  above  metals  may  be  kept  on  hand  to  furnish  a  variety  of  material  for 
the  analysis  of  "  unknowns."  Obtain  the  large  and  instructive  catalogues  of  dealers  in  chemicals  and 
chemical  apparatus. 

Apparatus  for  Student's  Table. 

Twelve  test  tubes,  4  inch. 

One  test  tube  stand. 

Two  test  tubes,  8  inch  and  large  diameter. 

Two  beakers,  4  and  6  ounces. 

Two  funnels,  3  and  4  inches  in  diameter. 

Two  evaporating  dishes,  3  and  4  ounces  capacity. 

One  platinum  foil,  one  inch  square. 

One  platinum  wire,  3  inches,  mounted  in  handle  of  glass 
tubing. 

One  pair  forceps,  of  steel  or  platinum. 

One  alcohol  lamp,  4  ounces,  or  Bunsen  burner. 

One  wash  bottle,  6  ounces  capacity. 

One  match  safe. 

A  blow  pipe. 

One  sand  bath,  a  shallow  sheet  iron  dish  containing  clean 
sand. 

One  ring  stand,  for  supporting  funnels,  evaporating  dishes 
sand  baths,  generating  flasks,  etc. 

Litmus  paper,  cut  into  strips  I  inch  long  and  4-10  inches 
wide,  and  kept  in  a  box  or  wide-mouthed  bottle. 

One  package  filter  paper,  4  inches  in  diameter. 


2O  QUALITATIVE    ANALYSIS. 

One  Marsh's  apparatus,  consisting  of  large  test  tube  fitted 
with  delivery  tube. 

One  solid  glass  stirring  rod,  6  inches  in  length  and  rounded 
at  the  ends. 

One  wash  bowl. 

A  towel. 

A  common  memorandum  book. 

A  blank  book  for  permanent  notes,  3  or  4  quires. 

The  student  should  also  provide  himself  with  an  apron 
made  of  strong  material,  and  large  enough  to  thoroughly  pro- 
tect his  clothing  from  injury  by  acids  and  other  chemicals. 

A  word  may  be  said  just  here  in  regard  to  the  cost  of  fit- 
ting up  the  laboratory  described  in  this  chapter. 

A  reliable  firm,  dealing  in  chemicals  and  supplies,  esti- 
mates the  cost  as  follows  : 

FOR  STUDENTS  TABLE. 

19  Reagents  Bottles        .        ..        -        .        .        .        .  $2.85 

Reagents  for  same       .         .         .       •  ...       .         .         .         .         .         .       1.52 

Apparatus       .  5-55 

Total  .'..•«  .  .   $9.92 

Cost  of  student's  tables  for  a  class  of  eight,  or  sixteen  if  divided 

into  two  sections     ...  ."  79-36 

FOR  GENERAL  TABLE. 

Reagent  Bottles          .....  .      $3.90 

Reagents  for  same                    . 12.60 

Dry  Reagents .         .  .        2.50 

Total  cost  for  well  equipped  laboratory  for  any  High  School  $98.36 

To  the  Student. 

The  student  must  not  suppose  that  his  acquirements  are 
to  be  confined  to  the  facts  and  principles  which  he  actually  dis- 
covers in  his  laboratory  work.  This  idea  would  defeat  the 
very  end  had  in  view  in  establishing  laboratory  courses,  that 
end  being  that  he  may  be  brought  into  living  sympathy  and 


THE    LABORATORY.  21 

personal  contact  with  the  researches  of  the  great  men  who 
have  built  up  the  body  of  chemical  science,  and  made  it  what 
it  now  is.  The  laboratory  work  has  not  accomplished  its  pur- 
pose unless  it  has  stimulated  the  desire  to  consult  authorities 
for  further  information.  Every  laboratory,  therefore,  should 
have  its  working  library,  larger  or  smaller,  of  standard  refer- 
ence books. 

A  few  volumes  are  here  mentioned  that  will  prove  to 
be  very  helpful  in  this  direction,  if  indeed  they  ought  not  to  be 
considered  as  indispensable  for  successful  work  :  — 

Prescott  and  Johnson's  Qualitative  Analysis,  latest  revised  edition. 

Smith's  Richter's  Inorganic  Chemistry. 

Remsen's  Chemistry,  larger  work. 

Elliot  and  Storer's  General  Chemistry. 

Shepard's  Chemistry. 

Roscoe  and  Schorlemmer's  Treatise  on  Chemistry. 


CHAPTER   IV. 

SOLIDS  AND  LIQUIDS. 

To  Change  Solids  into  Liquids. 

The  analytical  processes  developed  in  this  book  are  such  as 
can  only  be  carried  on  by  first  obtaining  the  substance  to  be 
examined  in  the  liquid  state.  It  therefore  becomes  necessary 
that  we  shall  be  able  by  one  method  or  another  to  reduce  all 
substances  to  a  state  of  solution. 

Of  substances 

(1)  Many  readily  dissolve  in  water, 

(2)  Some  not  so  readily, 

(3)  Others  not  at  all. 

The  first  are  spoken  of  as  soluble,  the  second  sparingly  sol- 
uble, and  the  third  insoluble. 

i.  Water  used  as  a  solvent  forms  a  physical  solution ;  that 
is  to  say,  the  substance  after  solution  is  chemically  the  same  as 
when  in  the  solid  state,  the  chemical  properties  of  the  solid 
being  retained  while  in  the  liquid  state. 

Solution:  —  Dissolve  2  grams  of  sugar  in  20  cc.  of  water;  taste  the  solu- 
tion ;  evaporate  to  dryness,  and  weigh  the  residue ;  taste  the  residue. 

Take  a  quantity  of  common  salt ;  notice  its  crystalline  structure  ;  taste  it ; 
treat  a  small  quantity  in  a  test  tube  with  water ;  treat  a  small  quantity  in  a 
test  tube  with  sulphuric  acid,  and  notice  the  color  and  odor  of  the  gas  given 
off ;  moisten  a  glass  rod  with  silver  nitrate  and  hold  it  in  the  escaping  gas. 

We  have  now  some  acquaintance  with  common  salt.  It  is  a  substance, 
(i)  highly  crystalline,  (2)  soluble  in  water,  (3)  has  a  peculiar  taste,  (4)  with 
sulphuric  acid  yields  a  colorless  gas  of  strong,  irritating  odor,  which  precipi- 
tates silver  nitrate  on  a  glass  rod. 

Now  evaporate  the  water  solution,  and  examine  the  substance  recovered 


SOLIDS    AND    LIQUIDS.  23 

by  the  operation.  Is  it  common  salt?  These  experiments  have  illustrated 
what  is  meant  by  a  physical  solution. 

The  varying  solvent  power  of  water  toward  different  substances,  as  well  as 
a  proper  conception  of  what  is  meant  by  a  saturated  solution,  may  be  under- 
stood by  the  following  experiments  : 

Take  10  cc.  of  distilled  water  in  a  test  tube;  add  I  gram  of  potassium 
carbonate  ;  shake  well,  and  if  it  dissolves  add  another  gram  of  the  salt ;  con- 
tinue this  until  no  more  will  dissolve. 

In  the  same  way  determine  the  solubilities  of  potassium  nitrate,  potassium 
sulphate,  calcium  sulphate,  sodium  chloride. 

2.  A  substance  insoluble  in   water  may  be  soluble  in  acids. 
In  this  case  chemical  action  takes  place,  there  is  a  loss  of  the 
original  properties,  and  a  chemical  solution  is  the  result. 

Take  a  small  piece  of  crystallized  limestone,  calc  spar ;  taste  it ;  boil  it  in 
water ;  treat  a  small  piece  in  a  test  tube  with  hydrochloric  acid,  and  notice 
odor  and  appearance  of  gas  given  off;  pass  the  gas  into  lime  water. 

Calc  spar  can  now  be  characterized  as  a  substance,  (i)  crystalline,  (2)  taste- 
less, (3)  insoluble  in  water,  (4)  soluble  in  hydrochloric  acid,  (5)  with  HC1 
yields  a  gas  which  renders  the  lime  water  turbid. 

Now  evaporate  the  solution  obtained  by  the  HC1,  and  ascertain  whether 
the  substance  obtained  is  calc  spar  or  not. 

The  experiment  shows  that  when  calc  spar  is  dissolved  in  HC1  it  loses  its 
character,  and  a  substance  has  been  formed  with  entirely  different  properties. 

The  acids  most  used  as  solvents  in  the  chemical  laboratory 
are  HC1,  HNO3,  and  nitro-hydrochloric  acid,  or  aqua  regia. 
These  are  successively  used  in  the  order  named,  using  in  each 
case  the  acid  diluted  in  water,  but  afterwards,  if  necessary, 
boiling  the  substance  in  the  concentrated  acid. 

NOTES  :  —  (a)  Whether  the  solvent  has  effected  a  solution  of  any  part  of  the  substance  may  be 
ascertained  by  evaporating  a  drop  or  two  of  the  liquid  on  platinum  foil.  If  any  has  dissolved,  a  solid 
residue  will  be  left  on  the  foil. 

(b)  The  acid  solutions  should  be  evaporated  nearly  to  dryness,  and  redissolved  in  water  before 
proceeding  with  the  analysis. 

(c)  Nitro-hydrochloric  acid  is  made  as  it  is  needed  by  mixing  three  parts  reagent  HC1  with  one 
part  of  HNOs.     The  reaction  may  be  as  follows,  SHCl+HNOs^NOCl+SCl+SHsO.     In  this  case  the 
active  agent  in  effecting  the  solution  is  the  nascent  chlorine. 

3.  A   third    condition    of   solubility    is    met    with    in   those 
substances  which  can  not  be  dissolved  in  water  or  acids.     Such 


24  QUALITATIVE    ANALYSIS. 

may  be  fused  on  the  platinum  foil  with  potassium  or  sodium 
carbonate.  This  breaks  up  the  given  substance  and  recombines 
it  in  a  form  which  is  now  soluble. 

For  example,  if  barium  sulphate  is  fused  with  sodium  carbonate  an  inter- 
change will  be.effected  producing  barium  carbonate  and  sodium  sulphate, 
barium  sulphate  +  sodium  carbonate  — 

barium  carbonate  -f  sodium  sulphate. 

The  sodium  sulphate  is  soluble  in  water,  and  the  barium  carbonate  in 
dilute  acid. 

It  will  further  be  noticed  that  the  metal  of  the  given  salt  is  to  be  found  in 
the  part  which  is  insoluble  in  water,  but  soluble  in  acid,  while  the  acid  radical 
is  found  in  the  water  solution. 

4.  Sometimes  the  alkali  hydroxides  are  useful  as  solvents. 

The  alkali  hydroxides  generally  form  solutions  which  in  character  may  be 
considered  as  lying  between  the  merely  physical  and  the  true  chemical  solu- 
tion ;  they  may  be  called  physico-chemical  solutions.  An  example  of  this  is 
seen  in  the  solution  of  silver  chloride  in  ammonium  hydroxide,  the  resulting 
solution  (NH3)3(AgCl)2  being  a  loose  union  of  the  two  compounds.  See 
page  38. 

To  Change  Liquids  into  Solids. 

It  is  sometimes  desirable  to  convert  substances  which  are 
in  solution  to  the  solid  state. 

This  may  be  done  by  evaporation  or  precipitation. 

In  the  former  case  the  solution  is  slowly  heated  in  an 
evaporating  dish  until  the  water  is  driven  off  and  the  solid 
substance  obtained  as  a  residue. 

Evaporate  100  cc.  of  a  solution  of  some  salt ;  weigh  the  residue,  and  deter- 
mine the  proportion  of  the  salt  to  the  water  in  the  solution. 

Evaporate  in  a  dish  of  known  weight  70  cc.  of  well-water  to  dry  ness ; 
weigh  the  residue,  and  calculate  the  per  cent  of  impurities  dissolved  in  the 
water. 

The  weight  of  the  residue  from  70  cc.  of  water  stated  in  milligrams  will 
be  at  the  same  time  the  number  of  grains  per  gallon.  Why? 

In  the  latter,  a  change  is  produced  by  which  a  new  sub- 
stance is  formed  insoluble  in  the  menstruum  present. 


SOLIDS    AND    LIQUIDS.  25 

Add  hydrochloric  acid  to  silver  nitrate ;  silver  chloride  is  formed,  insolu- 
ble in  water,  and  hence  it  appears  as  a  precipitate.  In  the  same  way  bring 
solutions  of  barium  chloride  and  potassium  carbonate  together  and  explain 
what  happens. 

As  in  dissolving  by  water,  evaporation  yields  a  substance 
of  the  same  chemical  composition  as  the  solution  ;  while  by 
precipitation  chemical  action  changes  the  composition  and 
character  of  the  substance. 


CHAPTER   V. 
CHEMICAL  EQUATIONS, 

What  is  a  chemical  equation  ? 
What  does  it  teach  ? 

Laboratory  Work.  —  Mix  the  substances  (in  solution  unless 
otherwise  stated)  together,  as  indicated  by  the  first  member  of 
the  equations  under  "  Examples  for  Practice,"  p.  29.  Observe 
carefully  what  takes  place,  and  having  learned,  on  good  author- 
ity,* the  composition  and  character  (whether  soluble  or  in- 
soluble) of  at  least  one  of  the  resulting  compounds,  finish  the 
equation. 

Do  not  make  the  writing  of  equations  simply  an  algebraic 
operation  for  this  will  often  lead  you  into  grave  errors  ;  but 
find  some  starting  point  either  in  observed  phenomena  or  good 
authority. 

It  would  be  well  if  some  system  of  notation  should  be 
adopted  by  which  precipitates,  gaseous  compounds,  and  solu- 
tions might  be  distinguished ;  e.  g.,  precipitates  may  be  under- 
scored, gaseous  compounds  marked  with  a  wavy  line  above  the 
symbol,  and  solutions  left  without  any  accompanying  mark. 

Three  Typical  Cases  are  here  discussed,  in  order  to  illustrate 
the  method  and  spirit  of  this  important  part  of  the  work  of  the 
student  in  chemistry. 

(i)  For  example,  having  mixed  solutions  of  barium  chlo- 
ride and  potassium  sulphate  together,  it  is  required  to  write  the 
equation. 

*  Prescott  and  Johnson's  "  Qualitative  Chemical  Analysis  "  may  be  consulted  as  authority  on  any 
or  all  the  reactions  suggested  in  this  book. 

26 


CHEMICAL    EQUATIONS.  2/ 

The  first  member  contains  the  substances  brought  together 

thus  : 

BaCl2+K2S04= 

When  the  substances  are  mixed  it  is  noticed  that  a  dense 
white  precipitate  is  formed,  and  the  memorandum  is  made  : 

BaCl2-|-K2S04=Pre.,  white,  crystalline. 

Reference  to  authority  teaches  that  the  precipitate  is 
barium  sulphate,  BaSO4,  and  the  equation  stands  : 

Baq+K2S04=BaS04 

Now  consider  (i)  in  forming  BaSO4  what  elements  have 
been  liberated?  and  (2)  will  these  unite  with  each  other? 
Two  atoms  of  Cl  are  set  free  from  the  BaCl2  and  two  atoms  of 
K  from  the  K2SO4,  just  enough  in  the  two  cases  to  make  two 
molecules  of  KC1.  As  potassium  chloride  is  a  well  known 
compound,  we  conclude  that  the  completed  equation  is  : 

BaCl2+K2S04=BaS04+2KCl. 

What  property  of  the  barium  sulphate  caused  it  to  be 
thrown  down  as  a  precipitate  ? 

Why  did  not  the  potassium  chloride  precipitate  ? 

Record  the  answers  to  the  last  two  questions  in  the  table 
of  solubilities  on  page  31. 

To  THE  STUDENT  :  —  It  is  of  the  utmost  importance  to  your  work  that  you 
early  acquire  the  habit  of  reducing  every  case  of  chemical  action  which  you 
study  to  the  form  of  the  equation.  By  doing  so  you  are  enabled  to  under- 
stand and  appreciate  many  elements  of  the  problem  which  otherwis?  would 
escape  your  notice. 

Some  of  the  points  thus  to  be  noticed  are :  the  relative  number  of  mole- 
cules of  each  substance  taking  part  in  the  transaction ;  the  relative  amounts 
by  weight,  and  the  relative  affinities  of  atoms  for  each  other.  Again,  by 
the  equation  may  oftentimes  be  determined  the  true  historical  succession 
of  events,  what  the  initial  movement  was,  what  influence  produced  that 
movement,  the  next  in  order,  and  so  on. 

As  a  means  of  mental  culture  and  discipline  there  is  no  more  fruitful  field 
than  the  writing,  discussion,  and  interpretation  of  the  chemical  equation. 


28  QUALITATIVE    ANALYSIS. 

When  was  the  chemical  equation  first  used  ?  Consult 
Roscoe  and  Schorlemmer's  Treatise  on  Chemistry,  vol.  Hi., 
pt.  i.,  p,  7. 

A  Second  Illustration.  —  Calcium  carbonate,  CaCO3,  in  the 
solid  state  is  treated  with  hydrochloric  acid. 

It  is  noticed  that  a  gas  is  given  off  which,  when  tested  (?), 
proves  to  be  carbon  dioxide,  CO2.  The  equation  will  then 
read  : 

CaC03+HCl=CO; 

Now,  the  HC1  must  have  been  separated  into  its  elements 
H  and  Cl.  The  CaCO3  yields  CO2,  and  the  question  arises  as 
to  the  character  of  the  compounds  resulting  from  the  recombi- 
nation of  these  elements,  Ca,  O,  H,  and  Cl ;  how  will  they  unite  ? 
Ca  and  H  will  not  unite  with  each  other.  Why  ?  H  and  O 
have  a  strong  affinity  for  each  other,  and  calcium  chloride  is 
a  well  known  compound.  The  conclusion  is  thus  forced  upon 
us  that  calcium  chloride  and  water  are  the  resulting  com- 
pounds. Further,  if  water  is  formed  there  must  have  been 
two  molecules  of  HC1  decomposed  for  every  one  of  the  CaCO3. 
These  two  molecules  of  HC1  will  furnish  the  two  atoms  of  H 
for  a  molecule  of  water,  and  at  the  same  time  two  atoms  of  Cl 
for  a  molecule  of  calcium  chloride.  The  equation  will  therefore 
stand : 

CaC03+2HCl=CO~2+H20+CaCl2. 

A  Third  Illustration.  —  A  solution  of  alum,  A12(SO4)3,  is 
treated  with  ammonium  carbonate,  (NH4)2CO3,  and  a  white 
precipitate  results.  Thus  : 

Al2(S04)3+(NH4)2C03=Pre.,  white,  gelatinous. 

Authority  teaches  that  when  these  two  compounds  in 
solution  are  brought  together  there  invariably  results  alum- 
inum hydroxide,  A12(OH)C, 

A12  (S04)  3+  (NH4)  2C03= AUOH) u 


CHEMICAL    EQUATIONS.  29 

It  is  now  evident  that  neither  the  element  H  nor  the  group 
OH  is  furnished  by  either  of  the  compounds  used,  and  that 
something  else  took  part  in  the  reaction.  The  only  other 
substance  present  is  water,  and  it  must  be  that  this  has  been 
decomposed.  Moreover,  there  must  have  been  six  molecules 
decomposed  to  yield  the  six  molecules  of  hydroxyl,  OH,  con- 
tained in  the  aluminum  hydroxide.  The  equation  will  then 
take  the  form  : 

Alg(S04),+(im4)8C08+6HaO=Al8(OH)B 

Again,  the  Al  of  the  precipitate  comes  from  the  decom- 
position of  one  molecule  of  A12(SO4)3.  This  would  set  free 
three  molecules  of  the  sulphuric  acid  radical,  SO4,  which  in 
turn  unites  with  NH4  to  form  (NH4)2SO4,  and  since  there  are 
three  molecules  of  SO4,  there  will  be  formed  three  molecules 
of  (NH4)2SO4,  making  it  very  certain  that  three  molecules  of 
the  (NH4)2CO3  were  broken  up.  These  latter  molecules  at  the 
same  time  set  free  three  molecules  of  CO2  and  three  atoms 
of  O.  The  three  atoms  of  O  unite  with  the  six  atoms  of  H  from 
the  water,  and  form  three  molecules  of  H2O.  The  completed 
equation  will  therefore  be  : 

A12(S04)3+3(NH4)2C03+6H20=A12(QH)(,+3(NH4),S04+3H,0+3CO;. 

Examples  for  Practice. 
FeCl8+KOH=  CaCl2+(NH4)2C03= 

MnCl2+(NH4)2S=  NH4Cl(solid)+H2S04= 

Pb(C2H302)2+HCl=PbCl2        HgCl2+H2S=HCl 
Cu(N03)2+H2S=  BaCl2+K2C03=BaCOs 

CaCl2+K2C03=KCl  HgCl2+  (NH4)  2S=HgS 

HgCl2+(NH4)2S=NH4Cl          FeCl3+K3FC6N6=Fe(FeC6N6) 
FeS04+K3FeC6N6=Fe3(FeC6N6)2 

NH4Cl(solution)+KOH(warm  slightly)  = 


3O  QUALITATIVE    ANALYSIS. 

Practical  Suggestions. 

The  most  scrupulous  neatness  of  work  table  and  apparatus  is  necessary  if 
correct  results  are  to  be  attained  in  chemical  analysis.  Especial  care  must 
be  taken  not  to  contaminate  the  chemicals  in  the  reagent  bottles,  either  by 
laying  down  the  stoppers  while  using,  allowing  the  bottle  to  stand  open,  or 
by  returning  material  after  it  has  once  been  taken  from  the  bottle. 

Use  small  quantities,  both  of  the  substance  to  be  analyzed  and  the  reagent. 
Add  reagents  cautiously,  drop  by  drop,  in  quantities  sufficient  for  complete 
precipitation  and  separation. 

When  the  work  requires  that  the  reagent  shall  be  added  "to  alkaline  or 
acid  reaction,"  use  the  test  paper  to  know  when  that  point  is  reached. 

Dilute  solutions  require  more  time  for  chemical  action  to  take  place.  In 
all  cases  be  deliberate ;  take  time  to  observe  all  that  occurs. 

Heat  facilitates  chemical  action  in  the  majority  of  cases,  although  some- 
times cold  is  necessary. 

A  most  valuable  as  well  as  necessary  feature  of  the  student's  work  is  the 
manner  in  which  he  keeps  his  notes.  Scientific  accuracy  requires  that  the 
notes  shall  be  taken  as  work  proceeds,  "while  the  test  tube  is  still  in  his 
hand."  They  should  record  the  conditions  under  which  the  test  was  made, 
all  the  phenomena  of  the  reaction,1  and  the  conclusions  to  be  drawn  from 
them:  (i)  what  has  been  done,  (2)  what  has  been  observed,  (3)  what 
conclusions  have  been  reached. 


SOLUBILITY. 


TABLE  OF  SOLUBILITIES. 

In  which  is  to  be  recorded  the  solubility  of  all  compounds  as 

fast  as  they  are  observed. 

Soluble  in  water,  S  ;  insoluble  in  water,  I  ;  insoluble  in  water,  but  soluble 

in  acids,  S'. 

o 

K 

•S 

. 

METALS. 

Chloride 

V 

3 
a, 
"3 

1 

jD, 

Carbonate 

Hydroxide 

1 

Nitrate 

Bromide 

a 

3 

2 

Sulphate 

Chlorate 

Chromate 

Ferrocyani 

Ferricyanic 

Phosphate 

Oxalate 

Ag 

Pb 

As 

Sb 

Sn 

Hg" 

Bi 

Cd 

Cu 

Fe" 

Fe'" 

Cr 

Al 

Co 

Ni 

Mn 

Zn 

Ba 

Ca 

Sr 

Mg 

K 

Na 

Li 

Columns  may  be  added  to  this  table  for  any  other  salts,  the  solubility 

of  which  it  is  desirable  to  record. 

_ 

CHAPTER   VI. 
GROUPING  OF  THE  METALS.* 

As  a  step  toward  the  discovery  of  schemes  of  analysis  by 
which  the  metals  most  commonly  occurring  can  be  identified  in 
unknown  compounds,  it  is  first  desirable  to  divide  them  into  a 
limited  number  of  well  defined  groups,  the  members  of  which 
shall  have  some  common  chemical  characteristics. 

The  commonly  occurring  metals  are  as  follows  :  f 
Ag',  As'",  Fe",  Fe'",  Ba",  K',  Pb",  Sb'",  Al'", 
Ca",  Na',  (Hg2)"  (Mercurous),  Hg"  (Mercuric),  Cr"', 
Sr",  (NH4)',  Mn",  Mg",  Sn",  Sn^,  Cu",  Bi'", 
Cd",  Zn",  Co",  Ni". 

A  common  reagent,  HC1,  is  chosen  and  its  behavior  with  a 
single  salt  of  each  of  the  above  metals  carefully  studied.  $ 

The  problem  before  the  student,  therefore,  is  to  answer 
the  question  : 

I.  How  are  salts  of  the  above  metals  affected  by  treating 
them  with  reagent  HC1  ? 

The  answer  to  this  question  can  only  be  found  by  making 
the  necessary  tests  in  the  laboratory. 

*  By  the  heading  of  this  chapter  it  is  not  to  be  understood  that  the  qualitative  chemist  investigates 
the  metals  themselves.  In  the  great  majority  of  cases  of  chemical  action  it  is  some  compound  of  the 
metal,  and  not  the  metal  in  the  elemental  state  that  is  involved.  The  whole  subject  of  the  grouping 
of  the  metals  and  the  subsequent  chapters  on  the  separation  of  the  metals  may  be  traversed,  and  the 
student  never  see  the  metals  as  such.  Indeed,  it  may  be  that  he  will  never  see  some  of  the  metals 
which  play  the  most  common  and  important  part  in  applied  chemistry.  By  their  very  nature,  such 
metals  as  calcium  and  barium,  potassium  and  sodium,  never  can  be  practically  used. 

t  The  valency  of  the  metals  as  indicated  in  the  above  list  should  be  fixed  in  mind. 

t  The  work  in  this  chapter  is  divided  into  eight  lessons,  indicated  by  the  wider  spacings.  Thus, 
the  first  lesson  would  be  simply  question  (i),  and  might  require  two  days  of  laboratory  and  class  room 
work ;  the  second  lesson  would  be  questions  (2)  to  (8)  inclusive ;  question  (9)  would  constitute  another 
long  lesson  ;  question  (10)  to  (16)  inclusive  another,  and  so  on. 

32 


GROUPING  OF  THE  METALS.  33 

About  five  cubic  centimeters  of  the  solution  to  be  tested  are  taken  in  a 
test  tube,  a  few  drops  of  the  reagent  added,  and  the  result,  precipitate  or  no 
precipitate,  noted. 

The  student's  work  and  note  book  will  proceed  as  follows : 

AgN03+HCl=Pre.,  white,  heavy. 

AgN03+HCl=AgCl+HN03. 

AsCl3+HCl=:No  Pre. 

FeS04+HCl=No  Pre. 

Fe2(S04)3+HCl=No  Pre. 

BaClj  may  be  found  in  solution  on  the  general  table.  From 
this  fact,  taken  with  another,  viz.,  that  if  a  reaction  occurred  between  any 
Ba  salt  and  HC1,  BaCl2  would  result,  we  conclude  that  no  salt  of  Ba  will  pre- 
cipitate with  HC1. 

K2S04+HCl=No  Pre. 

Pb(C2H302)2+HCl=Pre.,  white,  heavy,  crystalline. 

Pb(C2H302)2+2HCl=PbCl2+2HC2H302. 

SbCl3  may  be  found  in  solution,  and  hence  (see  Ba  above)  no 
Sb  salt  will  precipitate  with  HC1. 

The  work  should  be  thus  carried  on  until  at  least  one  salt  for  every  metal 
is  tested.  When  this  is  done  a  proper  response  to  question  (i)  can  be  given. 

2.  What  division  into  two  groups  is  suggested  by  (i)  ? 

3.  What  chlorides  are  insoluble  in  water  ? 

4.  What  constituent  element  of  the  HC1  enters  into  these 
precipitates  ? 

5.  What  class  of  salts  contains  this  element  ? 

6.  How  would  any  such  salts  affect   salts  of    Pb,  Ag,  and 
(Hg2)r/  ?     What  broad  generalization  is  here  reached  ? 

7.  What  constituent  element  of  the  salt  enters   into  these 
precipitates  ? 

8.  Would  any  salt  of  Pb,  Ag,  and  (Hg2)",  in  solution,  be  pre- 
cipitated by  HC1  ?     By  any  chloride  ?     What  broader  generali- 
zation is  here  reached  ? 

A  new  reagent,  hydrosulphuric   acid,  H2S,  is  now  taken, 
and  answers  found  to  a  question  similar  to  (i),  viz.  : 


34  QUALITATIVE    ANALYSIS. 

9.  How  do  the  given  salts  behave  when  treated  with  H2S  ? 

NOTE.  —  The  reagent  HaS  is  made  as  it  is  wanted  by  passing  the  gas  H^S,  generated  from  FeS 
and  HaSCh,  into  water  until  the  solution  smells  strongly  of  the  gas.     Equation. 

The  answers  to  question  (9)  obtained  by  the  different 
members  of  the  class  will  vary  somewhat,  from  the  fact  that,  in 
the  case  of  some  of  the  metals,  H2S  causes  a  precipitate  to 
form  very  slowly,  and  with  others  producing  simply  a  change 
of  color.  All  the  doubtful  cases  will  be  removed  if  a  small 
amount  of  HC1  be  used  with  the  H2S  as  reagent.  Let  the  stu- 
dent notice  how  promptly  the  lemon  yellow  arsenious  sulphide 
forms  when  the  solution  is  first  acidulated  with  HC1.  This 
raises  a  new  inquiry,  viz.  : 

10.  How  would  the  given  salts  be  affected  by  H2S  in  a  solu- 
tion to  which  HC1  has  been  added  ? 

The  work  done  on  (9)  and  (10)  has  illustrated  the  differ- 
ence that  may  exist  between  the  reagents  chosen  for  a  given 
work,  as  well  as  the  principle  on  which  such  reagents  are 
chosen.  Hydrogen  sulphide  will  not  effect  a  sharp  separation 
of  metals  into  groups,  because  of  its  indifferent  action  on  the 
salts  of  certain  metals,  but  when  combined  with  HC1  the  separa- 
tion becomes  clear  and  definite  ;  there  are  no  doubtful  cases. 

11.  Considering  questions  (2),  (9),  and  (10),  what  division 
into  three  groups  is  suggested  ? 

12.  What   sulphides  are  insoluble  in  H2O  ?      The  work  on 
question  (9)  has  answered  this. 

13.  What  sulphides  are  insoluble   in  H2O  and  HC1?     The 
work  on  (10)  has  answered  this. 

14.  What  constituent  element  of  the  H2S  enters  into  these 
precipitates  ? 

15.  What  class  of  salts  contains  this  element? 

1 6.  How  would  any  of  this  class  of  salts  change  salts  of  Fe, 
Mn,  Cu,  Pb,  Cd,  Ca,  or  Mg  ? 


GROUPING  OF  THE  METALS.  35 

17.  How  would  the  given  salts  behave  when  treated  with 
ammonium  sulphide,  (NH4)2S  ? 

1 8.  How  do  the  given  salts  behave  in  the  presence  of  ammo- 
nium carbonate,  (NH4)2CO3  ? 

19.  Would  any  other  carbonate  do  for  this  test  ? 

Suppose  it  were  required  to  make  barium  carbonate,  how  could  it  be 
done?  One  answer  to  this  question  would  be  to  combine  barium  chloride 
and  ammonium  carbonate.  A  broader  answer  would  be,  combine  barium 
chloride  with  any  soluble  carbonate.  Would  that  be  true?  A  still  broader 
answer  would  be,  combine  any  soluble  salt  of  barium  with  any  soluble  car- 
bonate. Would  that  be  true  ?  Could  any  barium  salt  be  combined  with  any 
carbonate  to  make  barium  carbonate? 

20.  Considering  all  you  have  learned,  how  may  Ba,  Ca,  and 
Sr  be  separated  from  all  the  others  ? 

21.  What  carbonates  are  soluble  in  water  ? 

22.  What  carbonates  are  insoluble  in  water  ? 

23.  How  are  Mg  salts  affected  by  (NH4)2  CO3  ?     Warm  the 
solution  a  little  if  necessary. 

24.  How  are  Mg  salts  affected  by  NH4C1  and  (NH4)2CO3  ? 
How  by  (NH4)2CO3  and  NH4C1  ?     What  facts  regarding  the 
solubility  of  Mg  salts  have  been  learned  ? 

25.  How  are  Mg  salts  affected  by  NH4C1  +  (NH4),CO3  and 
Na2HP04? 

26.  What  metals  may  constitute  a  First  Group  ?     A  Second 
Group  ?     A  Third   Group  ?     A  Fourth  Group  ?     Mg  may  be 
considered  as  a  member  of  the  Fourth  Group,  but   requiring  a 
reagent,  Na2HPO4,  peculiar  to  itself. 

27.  What  metals  are  left  to  constitute  a  Fifth  Group  ? 

28.  The  most   noticeable  characteristic  of  the  salts   of  the 
metals  of  the  Fifth  Group  is  their  failure  to  precipitate  when 
treated  with  any  common  reagent.     Why  ? 


3  QUALITATIVE    ANALYSIS. 

REVIEW. 

What  chlorides  are  insoluble  in  water  ? 
What  chlorides  are  soluble  in  water  ? 
What  sulphides  are  insoluble  in  water  ? 
What  sulphides  are  insoluble  in  HC1  ? 
What  sulphides  are  soluble  in  HC1  ? 

What  carbonates  are  insoluble  in  water  ? 
• 

What  carbonates  are  soluble  in  water  ? 

What  are  the  metals  of  the  First  Group  ?    Second  Group  ? 
Third?  Fourth?  Fifth? 

What  are  the  group  precipitates  of  First  Group  ?     Second 
Group  ?  Third  ?  Fourth  ?  Fifth  ? 

Classify  and  tabulate  these  group  precipitates  as  to  color, 
and  also  as  to  the  valency  of  the  metals  contained  in  them. 

The  above  questions  should  suggest  many  others  that  may  be  raised  by 
student  and  teacher,  in  order  thoroughly  to  review  the  work  thus  far  gone 


NOTE.  —  A  scientific  demonstration  does  not  consist  in  simply  making  a  single  experiment  and 
basing  a  conclusion  upon  it.  On  the  contrary,  no  true  scientist  will  announce  a  conclusion  until  he 
has  tested  it  by  many  and  repeated  trials.  Now,  the  work  done  in  the  laboratory  by  a  large  class 
makes  such  scientific  demonstrations  possible,  and  that  without  the  expenditure  of  a  large  amount  of 
time.  If  a  class  of  twenty  or  thirty  students,  doing  their  work  independently  of  each  other,  are 
agreed  in  regard  to  the  outcome  of  an  experiment,  or  series  of  experiments,  the  fact  thus  ascertained 
may  be  relied  upon.  A  doubt  expressed  by  one  or  more  of  the  class  calls  for  a  review  of  their  work, 
and  perhaps  of  the  work  of  the  whole  class. 


GROUPING    OF    THE    METALS. 


37 


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CHAPTER   VII. 
SEPARATION  OF  METALS  OP  THE  FIRST  GROUP. 

The  most  difficult  metals  to  identify  and  separate  are  those 
of  the  second  group,  and  hence  it  is  desirable  that  this  work 
shall  be  undertaken  only  after  considerable  experience  in  the 
handling  of  reagents  and  apparatus.  It  is  therefore  suggested 
that  instead  of  following  the  order  as  indicated  in  the  next  few 
pages,  the  student  study  the  separation  of  the  metals  of  the 
first  group,  then  pass  to  the  fourth  group,  and  from  that  to  the 
fifth,  the  third,  the  second  division  of  the  second  group,  and, 
last  of  all,  the  separation  of  the  elements  As,  Sb,  and  Sn. 

It  should  be  remembered,  however,  that  in  the  systematic 
analysis  of  unknown  compounds  the  order  which  has  been  de- 
veloped in  the  grouping  of  the  metals  must  be  strictly  adhered 
to  ;  that  is,  the  order  of  approach  must  always  be  first  group, 
second,  third,  fourth,  and  lastly  the  fifth  group.  Why  ? 

1.  What  are  the  metals  of  the  first  group  ? 

2.  In  accordance  with  what  fact  already  observed  may  they 
be  separated  from  all  other  metals  ? 

3.  What  then  is  the  group  reagent  ? 

4.  What  are  the  group  precipitates  f 

Before  5  and  6  are  answered  the  group  precipitates  should  be  filtered  and 
thoroughly  washed  with  pure  distilled  water.  The  hot  H20  and  NH4OH  may 
be  added  to  the  precipitate  on  the  filter. 

5.  How  are  these  affected  by  much  hot  water  ? 

6.  How  by  NH4OH  ?     See  under  4,  page  24. 

7.  What  is  the  composition  of  the  solution  which  is  obtained 
by  the  hot  H2O  ? 

8.  Of  the   remaining   chlorides,    which    one    is    soluble    in 
NH4OH  ? 


SEPARATION    OF    METALS    OF    THE    FIRST    GROUP.  39 

9.  Does  the  NH4OH  produce  any  change  in  Hg2Cl2  ? 

10.  From  5  and  6  find  a  direct  method  of   separating  the 
metals  in  this  group. 

11.  If  only  one  base  is  present  in  the  first  group  precipitate, 
NH4OH  will  determine  which  it  is.     How  ? 

Confirmatory  Tests. 

The  characteristic  behavior  above  described  of  these  first- 
group  metals  is  usually  sufficient  for  their  determination  ;  but, 
in  cases  of  doubt,  and  especially  in  the  examination  of  mix- 
tures, other  tests  may  be  made  which  shall  be  confirmatory  of 
the  original  analysis.  The  following  will  be  found  of  value  for 
this  purpose  : 

For  Lead.  —  Solutions  of  lead  salts  are  precipitated  by 
H2SO4,  sulphates,  H2S,  sulphides,  iodides,  chromates,  bromides, 
alkalies,  carbonates,  phosphates,  oxalates. 

The  student  should  not  fail  to  challenge  each  of  the  above  statements  with 
appropriate  tests,  recording  the  results,  such  as  color  and  general  appearance 
of  precipitates,  in  his  permanent  note-book. 

For  Silver.  —  Solutions  of  silver  salts  are  precipitated  by  the 
fixed  alkalies  (soluble  in  HNO3  and  HC2H3O2);  by  the  volatile 
alkali  hydrate  (soluble  in  excess  of  reagent);  by  hydrosulphuric 
acid,  alkali  sulphides  (soluble  in  HNO3),  bromides,  iodides 
(soluble  in  excess),  ferrocyanides,  ferricyanides,  carbonates, 
oxalates,  and  phosphates. 

For  Mercury  in  Mercurous  Solutions.  —  The  commonly  occur- 
ring mercurous  compounds  are  all  insoluble  in  water,  with  the 
exception  of  the  normal  nitrate,  and  hence  will  be  precipitated 
by  the  common  reagents. 

Alkali  sulphides  or  hydrosulphuric  acid  precipitate,  not 
mercurous  sulphide,  Hg2S,  but  HgS-j-Hg,  not  soluble  in  HNO3. 
(Does  this  last  distinguish  Ag  from  Hg  ?) 

12.  May  precipitations  occur  with  HC1  when  no  first  group 
base  is  present  ?     Yes  ;  consult  Prescott  and  Johnson's  "  Quali- 
tative Chemical  Analysis,"  fourth  revised  edition,  article  547. 


QUALITATIVE    ANALYSIS. 


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CHAPTER   VIII. 

OCCURRENCE  IN  NATURE  AND  USES  OF  METALS  OF  THE 
FIRST  GROUP. 

In  what  form  is  Ag  found  in  nature  ? 

Describe  one  process  of  separating  Ag  from  its  ores. 

What  salt  of  Ag  is  in  most  common  use  ?  What  is  it  used 
for? 

Fuse  a  piece  of  AgNO3  with  the  blow  pipe  on  charcoal. 

What  is  an  alloy  ? 

What  other  metal  besides  Ag  in  our  silver  coins  ?  Pro- 
portions of  the  two  metals? 

Are  English  coins  more  nearly  pure  than  ours  ? 

What  is  the  chemistry  of  the  photographic  process  ?  Ask 
the  photographer. 

Why  do  silver  coins  blacken  when  carried  in  the  pocket 
with  matches  ? 

Why  does  a  silver  spoon  blacken  which  has  been  used  in 
beating  eggs  ?  Try  the  experiment. 

What  is  the  effect  of  using  silver  drinking  cups  with  sul- 
phur waters  ? 

NOTE.  —  Silver  cyanide  is  a  good  solvent  for  silver  sulphide,  and  is  sometimes  used  for  cleansing 
tarnished  silver.     It  is  poisonous,  and  should  be  used  with  caution. 

In  what  form  is  Pb  found  in  nature  ? 

How  is  it  separated  from  its  ores  ?  Fuse  a  lead  salt  on 
charcoal. 

Some  of  its  physical  properties  ? 

What  is  the  effect  of  leaden  water  pipes  on  drinking 
water  ? 

41 


42  QUALITATIVE    ANALYSIS. 

What  is  litharge  ?     White  lead  ?     White  paint  ? 
What  is  the  "lead  "  of  lead  pencils  ? 
In  what  form  is  Hg  found  in  nature  ? 

How  is  Hg  separated  from  its  ores  ?  Heat  red  oxide  of 
mercury  in  a  closed  tube  of  hard  glass. 

What  is  corrosive  sublimate  ?  Calomel  ?  Lunar  caustic  ? 
Sugar  of  lead  ? 

To  a  solution  of  AgNO3,  containing  about  5  grams  of  the 
salt  in  100  cc  of  water,  add  a  few  drops  of  mercury,  and  allow 
it  to  remain  for  several  days.  The  silver  will  separate  in 
delicate  crystals. 


CHAPTER   IX. 
SEPARATION  OF  METALS  OF  SECOND  GROUP. 

1.  What  metals  constitute  Group  II.  ? 

2.  Pb  must   be    included    in    this  group,  as  it  is    not    com- 
pletely separated  as  a  chloride  in  the  first  group.     Why  ? 

3.  After  the  metals  of  the  first  group  have  been  set  aside, 
what  reagents  will  precipitate  those  of  the  second  group  and 
no  others  ? 

4.  What  are  the  precipitates  thus  formed  ? 

5.  How  are  these  precipitates  (filtered  and  washed)  affected 
by  yellow  ammonium  sulphide,  (NH4)2S2  ? 

NOTE.  —  Ordinary  colorless  ammonium  sulphide,  (NH-O^S,  which  has  stood  for  several  weeks  in 
the  laboratory  will  be  found  to  have  acquired  a  yellow  color,  and  its  composition  has  changed  to 
(NHOsS*. 

6.  What  is  the  effect  of   applying. HC1  to  the  filtrate  from 
(5)  (a)  if  something  has  dissolved  and  (b)  if  nothing  has  dis- 
solved ?   (Try  the  effect  of  adding  HC1  to  the  (NH4)2S2  by  itself.) 

7.  Of  the  group  precipitates  insoluble    in  (NH4)2S2,  which 
are  soluble  in  hot,  moderately  dilute  HNO3  ? 

8.  Of   the  nitrates  thus  formed,  which  are  precipitated  by 
H2SO4  ? 

9.  How  do  the  remaining  nitrates  behave  in  the  presence 
of  NH4OH  added  to  alkaline  reaction  ? 

Synopsize  the  work  in  this  group  as  far  as  you  have  gone. 

Separation  of  As,  Sb,  and  Sn. 

The  method  may  be  summarized  as  follows  : 

10.  The  sulphides  which  dissolved  by  (NH4)2S2,  (5),  may  be 
recovered  by  slightly  acidulating  with  HC1  which  has  first  been 

43 


44  QUALITATIVE    ANALYSIS. 

diluted  with  H2S.     Why?     The  As   is  thrown  down  as  As2S3 
yellow,  the  Sb  as  Sb2S5  orange,  and  the  Sn  as  SnS2,  yellow. 

11.  The  precipitates  are  filtered  and  washed. 

12.  A  minute  particle  of    KC1O3   is  immersed  in  the    pre- 
cipitate on  the  filter,  and  treated  with  a  few  drops  of  hot  HC1. 
The    As2S3  is  dissolved  as  H3AsO4,   the  Sb2S5  as  SbCls,  the 
SnS2  as  SnCl4. 

2KC103-HHC1=2KC1+C1204+2C1+2H20. 

13.  The  excess  of  Cl  is  driven  off  (why  ?)  by  evaporation  and 
the  solution  used  in  making  Marsh's  test. 

MarsJi's  Test. 

Generate  H,  using  Zn  and  diluted  H2SO4,  in  a  large  size 
test  tube  provided  with  a  suitable  delivery  tube,  and  when  the 
gas  is  freely  given  off  add  'the  solution  to  be  tested.  Com- 
pounds of  As  and  Sb  in  solution  will  be  reduced  by  the  H 
forming  the  gases  AsH3  and  SbH3. 

H3  As04+8H=4H20+ AsH3 . 

The  gas  thus  formed  is  introduced  into  a  solution  of  silver 
nitrate.  It  should  not  be  allowed  to  escape  into  the  air  in  any 
quantity  as  it  is  extremely  poisonous. 

A  colored  precipitate  in  the  AgNO3  solution  indicates  the 
presence  of  either  As  or  Sb.  If  the  former,  it  will  be  found  in 
the  filtrate,  as  H3AsOs,  after  the  excess  of  AgNO3  has  been 
precipitated  by  HC1  and  filtered  out.*  A  yellow  precipitate 
by  H2S  in  this  solution  is  evidence  of  As. 

The  Sb  enters  into  the  precipitate  as  Ag3Sb.  After 
digesting  this  precipitate  with  hat  HC1  (why  ?),  the  filtrate 
wUl  give  an  orange  precipitate  with  H2S,  evidence  of  Sb. 

If  Sn  is  present,  it  will  be  left  in  the  Marsh's  generator 
as  metallic  tin,  and  may  be  identified  by  filtering,  dissolving  in 

*  AgCl  is  sparingly  soluble  in  strong  HC1,  and  hence  the  acid  used  should  be  dilute. 


SEPARATION    OF    METALS    OF    SECOND    GROUP.  45 

hot  and  dilute  HC1  and  testing  the  solution,  SnCl2,  with  HgCl2. 
A  white  precipitate  of  mercurous  chloride,  Hg2Cl2,  or  a  gray 
precipitate  of  metallic  mercury,  Hg,  is  evidence  of  Sn. 

"  Spot  Tests  "  for  As  anil  Sb 

After  adding  the  solution  of  arsenious  acid  or  antimonic 
chloride  to  the  Marsh's  generator,  and  after  the  air  has  been 
completely  expelled  from  the  apparatus,  the  gas  may  be  lighted 
and  the  flame  held  in  contact  with  a  cold,  dry  porcelain  sur- 
face. Metallic  As  or  Sb,  as  the  case  may  be,  is  separated  and 
deposited  on  the  porcelain. 

The  deportment  of  these  spots  with  certain  reagents  is 
strikingly  different,  so  that  these  tests  become  important  factors 
in  the  detection  and  separation  of  these  elements.  Let  the 
student  ascertain  the  change  produced  by  the  treatment  of  the 
spots  by  the  following  reagents  : 

(a)  A  drop  of  hot  HNO3. 

(b)  A    drop    of    concentrated    alkaline    solution    of    sodium 
hypochlorite. 

(c)  Warmed  with  a  drop  of  yellow  ammonium  sulphide. 

(d)  Applying  (NH4)2C03  to  (c). 

(e)  Adding  HC1  to  (c). 

(f)  Compare  color,  lustre,  etc.,  of  spots.* 

Specimen  Pages  from  Student's  Note-Book. 

The  following  memoranda  and  equations  will  illustrate  the  condition  of 
the  student's  note-book  after  his  work  on  these  metals  in  the  laboratory  is 
completed. 

Arsenic. 

AsCl3+HCl=No  pre. 
AsCl3+HCl+H2S=Pre.,  yellow. 
2AsCl3+HCl+3H2S=As2S3+7HCl. 


*  See  Prescott  and  Johnson's  "Qualitative  Chemical  Analysis"  for  proper  authority  on  the 
work.  It  should  be  insisted,  however,  that,  the  class  make  the  above  experiments  with  known 
solutions  and  compare  results  before  looking  into  any  authority. 


46  QUALITATIVE    ANALYSIS. 

The  precipitate  is  filtered,  washed,  and  treated  on  the  filter  with  yellow 
ammonium  sulphide. 

As2S3+  (NH4)  2S2=Solution . 

As2S3+3  (NH4)  2S2=2  (NH4)  3  AsS3-f  S3. 

(NH4)3AsS3+(HCl+H2S)=Pre.,  yellow. 

2(NH4)3AsS3+6HCl+H2S=As2S3+6NH4Cl+4H2S. 

As2S3+HCl+KC103=:Solution. 

As2S3+10CH-8H20^2H3As04+10HCl-f-S3. 

H3As04+4Zn+4H2S04=H3As+4ZnS04+4H20. 

(Represent  the  last   reaction  by  two   equations   showing  the   successive 
steps.) 

AsH3+AgN03=Pre.,  black. 
AsH3+6AgN03+3H20=6Ag+H3As03+6HNO.,. 

The  excess  of  AgN03  is  removed  by  HC1  (AgN03+HCl=AgCl-}-HN03) , 
and  the  filtrate  is  treated  with  H2S. 
H3As03+H2S=Pre.,  yellow. 
2H3As03+3H2S=As2S3f6H20. 


Antimony. 
SbCl3+HCl=:No  Pre. 
SbCl3+HCl+H0S=Pre.,  orange  yellow. 
2SbCl3+HCl+3H2S=SKS2+7HCl. 

Precipitate  filtered  and  washed. 
Sb2S3+(NH4)«,S2=Solution. 
Sb2S3+3(NH4)2S2=2(NH4)3SbS4+S. 
2(NH,)3SbS4+6HCl+H,SrrSb2S,+6NH4Cl+4H9S. 

Precipitate  filtered,  washed,  and  treated  on  the  filter  with  KC103  and 
HC1. 

Sb2S5+6Cl+=2SbCl3+S5. 

6Zn+6H2S04=6ZnS04+12H. 

2SbCl3+12H^2SbH3+6HCl. 

The  last  two  equations  show  the  reaction  in  Marsh's  generator.  (What 
is  the  nature  of  the  work  to  be  done  in  changing  SbCl3  into  SbH3?  What 
chemical  agent  is  fitted  to  do  that  work?  How  much  H  is  needed  to  remove 
six  atoms  of  Cl?  How  much  H2S04  must  be  decomposed  to  furnish  this? 
etc.,  etc.) 


SEPARATION    OF    METALS    OF    SECOND    GROUP.  47 

SbH3+3AgN03=Ag3Sb+3HN03. 

AgaSb+6HCl=3AgCl+SbCl3+6H. 

2SbCl3+3H2S=Sb2S3+6HCl. 

Tin. 

SnCl2+HCl=No  Pre. 

SnCl2+HCl+H2S=Pre.,  brown. 

SnCl2+HCl+H2S=SnS+3HCl. 

SnS+(NH4)2S2=(NH4)2SnS3. 

(NH4)2SnS3+2HCl+H2S=SnS2+2NH4Cl+2H2S. 

SnS24-4Cl=SnCl4+S2. 

SnCl4+2Zn+2H2S04=Sn+4HCl+2ZnS04. 

Sn+2HCl=SnCl2+2H. 

SnCl2+2HgCl2=Hg2Cl2+SnCl4. 

Hg2Cl24-SnCl2=Hg+SnCl4. 

Confirmatory   Tests. 

For  Cadmium.  —  Solutions  of  Cd  salts  are  precipitated  by 
NaOH,  NH4OH  (soluble  in  excess),  (NH4)2S,  KCN  (soluble 
in  excess),  phosphates  (soluble  in  acids),  oxalates,  ferrocya- 
nides  (soluble  in  HC1  and  NH4OH),  ferricyanides  (with  same 
solubilities  as  ferrocyanides). 

For  Copper.  —  A  clean  iron  nail  or  knife  blade  immersed 
for  a  few  minutes  in  a  solution  of  copper  salts  acidulated  with 
HC1  separates  metallic  Cu.  Equation  ? 

NaOH  or  KOH  added  to  copper  salts  precipitate  blue 
Cu(OH)2  which,  on  boiling,  changes  to  black  Cu3O2(OH)2 ; 
NH4OH  first  forms  a  greenish,  then  a  bluish  precipitate  which 
dissolves  in  excess  to  a  deep  blue  solution,  a  very  delicate  test, 
yielding  results  in  solutions  containing  one  part  of  Cu  to  one 
hundred  thousand  parts  of  water. 

Copper  salts  are  precipitated  by  (NH4)2CO3  (soluble  in 
excess),  K2CO3,  sulphides  (soluble  in  HNO3),  phosphates,  oxal- 
ates, chromates,  alkali  cyanides  (soluble  in  excess),  ferrocya- 
nides, ferricyanides,  iodides. 


48  QUALITATIVE    ANALYSIS. 

For  Bismuth.  —  Study  the  action  of  the  following  reagents 
on  a  known  solution  of  a  bismuth  salt  and  record  the  results 
for  future  use  as  confirmatory  tests  :  water  (in  acidulated  solu- 
tions), alkalies,  carbonates,  H2S  and  sulphides,  chromates, 
phosphates,  oxalates,  KI,  KBr,  KCN,  ferrocyanides,  ferricya- 
nides. 

For  Mercury  in  Mercuric  Compounds.  —  The  black  precipitate 
of  HgS,  insoluble  in  HNO3,  is  dissolved  by  nitro-hydrochloric 
acid  and  the  solution  treated  with  stannous  chloride,  SnCl2. 
A  white  precipitate  is  Hg2Cl2  ;  the  gray  precipitate  which 
finally  appears  is  metallic  mercury,  Hg. 

(1)  HgS+Cl2=HgCl2+S. 

(2)  2HgCl2+SnCl2=Hg2Cl2+SnCl4. 

(3)  Hg2Cl2+SnCl2=2Hg+SnCl4. 

A  bright  strip  of  copper  immersed  in  a  solution  of  mer- 
curic salt  will  be  covered  with  metallic  mercury.  Another 
characteristic  test  for  mercuric  salts  is  the  production  of  the 
yellowish  red  mercuric  iodide,  HgI2,  soluble  by  excess  to  a 
double  iodide,  HgI2(KI)2. 


Synoptical  View  of  Separation  of  the  Metals  of  Second  Group. 

From  the  work  on  pages  43  to  47  make  a  synopsis  of  the 
work  6f  separation  in  this  group.     See  p.  40,  and  note  on  p.  56. 


CHAPTER    X. 
OCCURRENCE  AND  USES  OP  SECOND  GROUP  METALS. 

In  what  form  is  As  found  in  nature  ?  How  separated 
from  its  ores  ? 

Heat  small  pieces  of  the  mineral  realgar  or  orpiment  in 
the  bottom  of  a  closed  glass  tube.  If  it  is  not  too  strongly 
heated,  metallic  arsenic  will  be  left  in  the  bottom  of  the  tube 
and  the  sulphides  of  arsenic  will  sublime  on  the  sides. 

In  another  tube  put  a  minute  piece  of  arsenic  trioxide,  and 
just  above  it  a  small  piece  of  charcoal.  Heat  gently.  Explain 
the  reaction. 

What  is  the  "  arsenic  "  of  the  drug  store  ? 
Study  the  properties  and  uses  of  As. 
What  is  Paris  Green? 

Especially,  study  the  uses  of  As  as  a  pigment  in  wall 
paper,  children's  hose,  etc. 

Composition  and  uses  of  Fowler's  solution  ? 

The  antidote  for  arsenical  poisoning  is  freshly  precipitated 
ferric  hydroxide,  Fe  (OH)3.  It  forms  an  insoluble  compound 
with  the  arsenic  in  the  stomach.  Prove  that  this  is  true  by 
the  following  experiment  :  — 

Treat  a  dilute  solution  of  H3AsO3  with  freshly  precipitated 
Fe  (OH)3  (in  excess),  filter  and  test  the  filtrate  for  As. 

How  does  Sb  occur  in  nature  ?     How  separated  ? 

What  is  tartar  emetic  ?     Cream  of  tartar  ?     Butter  of  anti- 


mony ? 


49 


5O  QUALITATIVE    ANALYSIS. 

In  what  form  is  Sn  found  ?  How  is  it  prepared  for  com- 
merce ? 

Its  properties  and  uses  ?  What  is  block  tin  ?  Tin  plate  ? 
Pewter  ?  Solder  ?  Britannia  ?  German  silver  ? 

Occurrence  of  Bi  ?  Its  chief  uses  ?  What  are  fusible 
metals  ? 

Occurrence  of  Cu  ?     Its  properties  and  uses  ? 

Separate  the  Ag  of  a  ten  cent  piece  from  the  Cu  ? 

Describe  the  process  of  electroplating ;  of  electrotyping. 

What  is  brass  ?     Bronze  ?     Bell  metal  ? 

Occurrence  of  Cd  ?     Its  properties  and  uses  ? 

NOTE.  —  Many  of  the  rare  metals,  such  as  gold,  platinum,  palladium,  iridium,  and  tellurium,  are 
found  in  this  group.     Their  sulphides  are  insoluble  in  water  and  dilute  acids. 

Gold  which  occurs  mostly  in  the  native  state  may  be  dissolved  by  nitro-hydrochloric  acid  to  auric 
chloride,  AuCl3.     If,  now,  ferrous  sulphate  be  added  to  this  solution,  metallic  gold  will  be  separated 
in  a  finely  divided  state.     This  may  be  fused  to  a  yellow  bead  on  charcoal. 
2AuCl3+6FeS04=2Au+2Fe2(S04)3+Fe2Cl6. 

For  other  tests,  for  this  and  the  other  noble  metals,  consult  the   larger  works  on  qualitative 
chemistry. 


CHAPTER    XL 

« 

SEPARATION  OF  METALS  OF  THE  THIRD  GROUP. 

Make  experiments  as  suggested  in  the  table  below,  record- 
ing the  results  in  the  appropriate  places  as  Pre.  (precipitate)  or 
No  Pre.  (no  precipitate),  marking  any  precipitates  which  dis- 
solve in  excess  of  reagents  by  a  star,  thus,  Pre.* 


REAGENTS    ADDED 

TO   SOLUBLE   SALTS  OF 

KOH  or  NaOH/ 

i 

"o> 

O 

51 

3 

g 

1 

a 

eg 

PQ 

o 

5 

1 

.'' 

»     3 

in  excess 

NH4OH,     in     ex-, 

cess 

NH4C1+NH4OH, 

(excess) 

(NH4)2CO3 

(NH4),>S 

HC1  +H2S 

Questions  on  the  Table  Work. 

What  reagent  precipitates  all  the  metals  of  the  third  group 
and  not  those  of  the  fourth  ? 

How  are  these  metals  separated  from  those  of  the  second 
group  ? 

S1 


52  QUALITATIVE    ANALYSIS. 

In  mixtures  of  second  and  third  group  salts,  the  latter 
will  be  found  in  the  filtrate  from  the  second  group  precipitate 
and  hence  necessarily  acid. 

This  being  so,  it  is  proper  to  consider  (i)  what  effect  this 
acid  will  have  on  the  proposed  group  reagent,  and  (2)  how  this 
may  be  counteracted.  The  choice  of  NH4OH  for  the  latter 
purpose  will  necessitate  further  inquiries,  viz., 

Will  NH4OH  precipitate  any  of  the  metals  of  this  group  ? 

Will  NH4OH  precipitate  any  salt  beyond  this  group  ? 

How  may  this  be  prevented  ? 

What  metals  of  this  group  are  precipitated  by'&H4Cl  and 
NH4OH  ? 

The  above  work  has  led  to  the  division  of  the  group  into 
two  sub-groups,  the  first  containing  the  triad  elements,  Fe,  Cr, 
Al,  and  the  second  those  having  a  valence  of  two ;  but  the 
method  has  this  imperfection,  that  iron  salts  in  the  ferrous 
condition  do  not  precipitate  readily  with  NH4C1  and  NH4OH, 
ferrous  hydroxide  being  somewhat  soluble  in  NH4CL  In  order, 
therefore,  that  both  forms  of  iron,  ferrous  and  ferric,  shall 
precipitate  together,  the  former  is  oxidized  to  the  ferric  condi- 
tion before  applying  the  reagents  NH4C1  and  NH4OH. 

These  facts  make  it  necessary  that  we  should  turn  aside 
and  make 

A  Study  in  Oxidation. 

It  is  first  necessary  to  be  able  to  distinguish  readily  be- 
tween ferrous  and  ferric  compounds.  The  following  table 
gives  two  characteristic  tests  for  this  purpose. 


KEAGEKTS   ADDED 

TO   SOLUTIONS. 

KCNS 

KsFeCeNe 

Ferric 

Ferrous 

Blood  red  solution. 
Green  solution. 

No  change. 
Blue  precipitate. 

Let  the  student  write  the  equations  for  these  tests. 


SEPARATION    OF    METALS    OF    THE    THIRD    GROUP.  53 

Oxidation. 

The  Meihod.  —  Take  two  cubic  centimeters  of  a  solution  of 
a  ferrous  salt  (identified  to  be  such  by  the  proper  tests)  in  a 
test  tube  and  add  two  or  three  drops  of  nitric  acid.  Boil  for  a 
minute  or  two  or  until  the  brown  fumes  pass  away.  The  solu- 
tion should  now  give  the  test  for  the  ferric  condition.  By  sev- 
eral tests  determine  the  least  amount  of  nitric  acid  necessary 
to  accomplish  the  oxidation. 

NOTE. —An  reaction  very  similar  to  this  occurs  in  the  "brown  ring  test"  for  nitric  acid,  and  its 
thorough  study  may  be  reserved  until  that  point  is  reached.  The  equation  for  the  oxidation  is  as 
follows  : 

3FeS04+4HN03=Fe(N03)3+Fe2(S04)3+NO+2H20. 

In  this  connection  several  points  should  be  noticed : 

1.  The  value  of  HNO3  as  an  oxidizing  agent  due  to  its  un- 
stable character  (?)  and  its  large  proportion  of  oxygen. 

2.  The  effect  which  the  mere  presence  of  an  oxidizable  sub- 
stance, such  as  FeSO4,  produces  on  the  HNO3. 

3.  The  evolution  of  the  brown  vapors,  which  is  always  the 
sign  or  indication  that  an  oxidizing  agent  and    an    oxidizable 
substance  have  been  brought  together. 

4.  Iron  in  the  filtrate  from  second  group  is  necessarily  fer- 
rous, as  hydrosulphuric  acid,  H2S,  acts  on  ferric  salts  as  a  re- 
ducing agent. 

2FeCl3+H2S=2FeCl2+2HCl+S. 

Make  several  tests  to  prove  this. 

Tests  for  Fe,  Cr,  and  Al.  —  The  salts  in  solution  have  been 
treated  with  HNO3,  NH4C1,  NH4OH ;  the  hydroxides, 
Fe(OH>,  Cr(OH)8,  and  A1(OH)3  have  been  precipitated; 
the  precipitates  have  been  filtered  and  washed. 

Now  pierce  the  point  of  the  filter  with  a  glass  rod,  and, 
with  a  small  quantity  of  pure  water,  wash  the  precipitate  into 
a  test  tube.  Divide  this  precipitate  into  three  portions. 

For  Iron.  —  Dissolve  one  portion  in  HC1  and  ascertain  (a) 
how  the  solution  is  changed  by  KCNS,  and  (b)  how  the  result- 
ant solution  is  changed  by  HgCl2. 


54  QUALITATIVE    ANALYSIS. 

For  Chromium.  —  Fuse  a  second  portion  of  the  hydroxide, 
supposed  to  be  Cr(OH)3,  on  the  platinum  foil  with  an  equal 
portion  each  of  dry  Na2CO3  and  KNO3.  A  yellow  mass  indi- 
cates Cr. 

2Cr(OH)3+Na2C03+2KN03=K2Cr04+Na2Cr04+2NO+C02+3H20. 

Dissolve  this  yellow  mass  in  H2O,  acidify  with  HC2H3O.2 
and  add  Pb(C2H3O2)2 ;  a  dense  yellow  precipitate  is  a  further 
indication  of  Cr. 

For  Aluminium.  —  Dissolve  the  third  portion,  supposed  to  be 
A1(OH)3,  in  KOH  and  add  NH4C1  in  excess,  or,  slightly  acid- 
ulate with  HC1  and  add  excess  of  (NH4)2CO3.  A  precipitate  in 
either  case  is  A1(OH)3. 

Tests  for  Mn,  Zn,  Co,  Ni.  —  ln  case  HNO3,  NH4C1  and 
NH4OH  have  been  applied  to  salts  of  metals  of  this  group  and 
no  precipitate  has  resulted,  what  is  the  effect  of  adding 
(NH4>S  ? 

Of  the  sulphides  thus  produced,  which  are  soluble  in  HC1? 

How  do  the  chlorides  thus  formed  behave  in  the  presence 
of  an  excess  of  KOH  ? 

How  is  the  Zn  solution  affected  by  adding  (NH4)2S? 

Fuse  the  insoluble  Mn(OH)2  on  the  platinum  foil  with 
KNO3  and  Na2CO3  and  note  the  bright  green  mass. 

3Mn(OH)2+4KN03-|-Na2C03=2K2Mn04+Na2Mn04+4NO+C02+3H20. 

Make  a  transparent  bead  on  the  platinum  wire  with  borax 
and  moisten  with  the  sulphides  of  Co  and  Ni.  On  further 
heating,  characteristic  colors  will  be  developed,  blue  for  Co  and 
brownivr  Ni. 

Confirmatory  Tests. 

For  Ferrous  Sa/fs.  —  Solutions  of  ferrous  salts  are  precipi- 
tated by  KCN,  reddish  brown ;  K3FeC6NG,  dark  blue,  (how 
does  this  precipitate  behave  when  treated  with  NaOH?); 
K4FeCcN6,  bluish  white  ;  (NH4)2CO3,  white  at  first,  but  soon 
changing  to  reddish  brown  ;  Na2HPO4,  white  to  bluish-white. 
KCNS  produces  no  change  in  ferrous  salts  free  from  ferric. 


CONFIRMATORY    TESTS.  55 

For  Ferric  Salts.  —  Solutions  are  precipitated  by  alkali 
hydroxides ;  alkali  carbonates ;  ammonium  sulphide ;  ferro- 
cyanides  (Prussian  blue).  Disodium  hydrogen  phosphate, 
Na2HPO4,  forms  a  yellowish  white  precipitate,  if  no  free  acid 
is  present,  easily  soluble  in  mineral  acids,  insoluble  in  acetic 
acid. 

Characteristic  colored  solutions  are  formed  by  sulphocya- 
nides,  blood  red  ;  ferricyanides,  green  or  brown  ;  acetates,  dull 
red  ;  sulphites,  red. 

Reducing  agents  change  ferric  into  ferrous  salts  ;  test 
with  HC1  and  Zn  ;  with  H2S  ;  with  KI.  Make  the  green  solu- 
tion by  treating  FeCl3  with  K3FeC6N6  and  then  add  a  reducing 
agent,  such  as  H2S  (?). 

For  Chromium.  —  Chromic  hydroxide,  Cr(OH)3  is  precipi- 
tated from  chromic  salts  by  NH4OH,  KOH,  (NH4)2S,  and 
alkali  carbonates. 

For  Aluminum.  — Aluminum  hydroxide,  A1(OH)3,  is  precipi- 
tated from  solutions  of  salts  by  (NH4)2S,  NH4OH,  KOH 
(soluble  in  excess  and  reprecipitated  by  NH4C1),  and  by  alkali 
carbonates.  Of  a  grayish  white  color,  gelatinous,  floating  in 
every  part  of  the  menstruum  in  which  it  forms,  this  precipitate 
is  easily  recognized  and  readily  distinguished  from  all  others. 

For  Manganese.  —  Manganese  forms  two  classes  of  salts, 
manganous  and  manganic,  the  latter  being  somewhat  unstable. 
Manganous  salts  are  precipitated  by  alkali  hydrates,  white, 
turning  to  brown  in  the  air  ;  (NH4)2S,  flesh  color;  alkali  car- 
bonates, white  to  brown,  and  Na2HPO4,  white. 

For  Zinc.  —  Of  zinc  salts,  the  acetate,  bromide,  chloride, 
chlorate,  chromate,  iodide,  nitrate,  and  sulphate  are  soluble  in 
water ;  those  insoluble  in  water  are  soluble  in  acids.  The  sol- 
uble salts  have  an  acid  reaction,  metallic  taste,, and  are  poison- 
ous. 

Zinc  salts  are  precipitated  by  all  alkali  hydroxides,  white 
(soluble  in  excess);  by  (NH4)2S  ;  by  alkali  carbonates,  white; 
KCN,  ferrocyanides,  white;  ferricyanides,  yellowish. 


56  QUALITATIVE    ANALYSIS. 

SALTS    OF 

NICKEL,  |  COBALT, 

In  crystalline  condition  and  in  solution, 
green,  \  red, 

these  dehydrated, 

yellow,  |  blue. 

Treated  with  fixed  alkali  hydroxides, 
green  precipitate,  \  blue  precipitate  ; 

the  hydroxide  heated, 
green  precipitate,  \     red  precipitate  and  finally  brown. 

Treated  with  ammonium  hydroxide, 
greenish  precipitate,  \  blue  precipitate. 

Treated  with  ammonium  hydroxide  in  excess, 
blue  solution,  \  reddish  solution. 

Treated  with  alkali  carbonates, 
pale  green  precipitate,  \  violet  red  precipitate. 

Phosphates.  —  The  presence  of  the  phosphates  in  mixture 
with  third  group  salts  complicates  the  analysis  from  the  fact 
that  the  phosphates  of  the  fourth  group  metals  can  only  be 
held  in  solution  by  acids,  and  hence,  when  the  solution  is  ren- 
dered alkaline  by  NH4OH  in  the  third  group,  Ca,  Ba,  or  Sr,  are 
precipitated.  Whether  phosphates  are  present  or  not  may  be 
ascertained  by  the  test  with  ammonium  molybdate  (see  phos- 
phoric acid).  If  found  to  be  present,  their  separation  may  be 
studied  from  a  larger  work.  See  Prescott  and  Johnson,  fourth 
revised  edition,  article  305. 

Synoptical  View  of  the  Separation  of  Third  Group  Metals. 

Condense  the  foregoing  work  into  a  complete  synopsis, 
similar  to  that  on  page  40,  of  the  separations  in  this  group. 

NOTE:  —  These  synopses  will  lack  clearness  and  their  value  be  largely  destroyed  if  the  attempt 
is  made  to  exhibit  all  of  the  details  of  the  work,  confirmatory  tests,  etc.  Only  the  principal 
resulting  compounds  are  to  be  shown.  It  ought  also  to  be  said  that  these  synoptical  views  will  only 
possess  value  to  the  student  in  proportion  as  they  are  the  result  of  his  own  ingenuity  and  labor. 
Such  work  merely  copied  from  others  is  almost  wholly  valueless. 


CHAPTER    XII. 

OCCURRENCE  IN  NATURE  AND  USES  OF  THIRD  GROUP 

METALS. 

What  metal  is  of  the  most  importance  to  man  ? 

In  what  form  is  Fe  found  in  nature  ? 

Name  the  most  valuable  ores. 

For  what  is  iron  pyrites  valued  ? 

Describe  the  process  of  smelting  Fe  from  its  ores. 

What  is  steel  ?     How  is  it  made  ? 

What  is  cast  iron  ?  Wrought  iron  ?  How  are  these  varie- 
ties made?  What  is  meant  by  the  " temper"  of  steel? 

What  is  malleable  iron  ?     Pig  iron  ? 

What  is  the  third  most  plentiful  and  widely  occurring 
element  ?  How  prepared  ? 

AlCl3+3Na  =  Al+3NaCl. 

What  is  the  probability  that  it  will,  some  time  replace  iron 
for  many  purposes  ? 

What  can  you  say  of  the  hardness  of  the  metal  Al  ? 
Its  malleability  ?  Ductility?  Tenacity?  Its  specific  gravity  ? 
Its  power  to  conduct  electricity?  Its  tarnishing  in  the  air? 

What  are  some  of  its  prospective  uses  ? 

What  is  alum  ?  For  what  purpose  is  it  introduced  into 
baking  powders  ?  How  may  you  detect  its  presence  ? 

What  is  topaz?  Beryl?  Turquoise?  Ruby?  Emery? 
Sapphire  ? 

What  is  common  clay  ?  Bricks  made  from  some  kinds  of 
clay  are  red.  Why  ? 

How  does  Cr  occur  in  nature  ?  What  is  the  principal 

57 


58  QUALITATIVE    ANALYSIS. 

use  of   the  metal  ?     What  is  chrome  alum  ?     Chrome   green  ? 
Chrome  yellow  ? 

Occurrence,  properties,  and  uses  of  Ni  ? 

What  is  the  composition  of  our  five  cent  coins?  Answer 
the  last  question  by  dissolving  a  " nickel"  in  HNO3  and  de- 
termining the  metals  the  coin  contains. 

Occurrence,  properties,  and  uses  of  Mn  ? 

Study  the  action  of  a  solution  of  K2Mn2O8  on  the  organic 
matter  in  impure  drinking  water. 

How  is  Zn  found  in  nature?  The  most  important  of  its 
ores  ?  How  separated?  Its  properties  and  uses  ? 

How  is  Zn  utilized  in  the  laboratory  ?  What  are  the  prin- 
cipal impurities  in  commercial  Zn  and  how  removed  ?  What  is 
galvanized  iron  ? 

Heat  a  small  piece  of  Zn  on  charcoal  with  the  blowpipe, 
using  the  oxidizing  flame.  The  white  fumes  of  zinc  oxide, 
"  philosopher's  wool,"  will  be  seen,  and  the  charcoal  will  be  cov- 
ered with  a  film  which  is  yellow  while  hot,  but  becomes  white 
when  cool. 

Repeat  the  same  experiment,  using  a  piece  of  lead. 


CHAPTER    XIII. 
SEPARATION  OF  METALS  OF  FOURTH  GROUP. 

Perform  the  work  suggested  below,  recording  the  results 
(pre.  or  no  pre.)  in  the  proper  spaces. 


REAGENTS    ADDED 

TO   SOLUBL 

Ca 

E   SALTS  OF 

Ba 

Sr 

Mg 

KOH  or  NaOH 

NH4OH 

NH4C1  and  NH4OH 

Carbonates 

NH4C1  and  Carbonates 

Sulphates  or  H2S04 

(NH4)2C204 

Chromates,  K2Cr207 

Na2HP04 

Questions  on  tlie  Table  Work. 

1.  What  salts  are  precipitated  by  KOH  ? 

2.  What  salts  are  precipitated  by  NH4OH  ? 

3.  How  do  Mg  salts  behave  when  (NH4)2CO8  is  added  to 
them,  (a)  in  dilute  solutions  of  the  Mg  salts,  and  (b)  in  con- 
centrated solutions  ? 

59 


6O  QUALITATIVE    ANALYSIS. 

4.  How  in   both    cases   when    NH4C1    and   (NH4)2CO3    are 
added  ? 

It  is  evident  that  (NH4)2CO3  might  be  used  as  the  group 
reagent,  at  least  for  Ba,  Ca,  and  Sr. 

5.  What  would  be  the  effect  on  this  reagent  if  the  given  salt 
were  acid  or  contained  free  acid  ? 

6.  How  could  this  be  avoided  ? 

7.  If  NH4OH  were  added  to  neutralize  any  free  acid  mixed 
with  the  salt  would  this  precipitate  any  member  of  this  group  ? 

As  Mg  precipitates  as  a  carbonate  only  in  concentrated 
solutions  it  is  best  to  prevent  its  formation  as  such.  This  pre- 
caution the  chemist  always  takes. 

8.  How  can  this  be  done  ? 

9.  How  are  the  fourth  group  salts  affected  by  the  addition  of 
NH4C1,  NH4OH  and  (NH4)2CO3? 

10.  How  do  Mg  salts  behave  when,  besides  the  above  reagents 
(9),  Na2HPO4is  added? 

11.  Of  the  carbonates  formed  in  (9)  (filtered  and  thoroughly 
washed),  which  are  soluble  in  HC2H3O2  ? 

12.  Of  the  acetates  thus  formed,  which  will  precipitate  with 
K2Cr2O7? 

13.  Of  the  remaining  acetates,  which  would  be  precipitated 
by  CaSO4? 

14.  Would  (13)  be  any  positive  test  for  Ca  ? 

15.  Which  of  the  remaining  acetates,  as  in  (13),  would  be 
precipitated  by  K2SO4,  or  dilute  H2SO4  ? 

CaSO4  is  soluble  in  400  parts  of  water;  SrSO4  in  7,000 
parts;  (NH4)2  C2O4  will  give  a  visible  precipitate  in  solutions 
containing  one  part  of  a  calcium  salt  to  21,600  parts  of  H2O. 

The  facts  stated  above  suggest  a  method  of  separating  Sr 
and  Ca,  viz.,  that  when  the  acetate  solution  has  been  treated 
with  K2SO4  there  still  remains  enough  of  the  CaSO4  in  solu- 


SEPARATION    OF    METALS    OF    FOURTH    GROUP.  6l 

tion  to  give  a  test  with  (NH4)2C2O4.  The  CaSO4  solution  must 
first  be  carefully  neutralized  with  NH4OH.  (Why  neutralized  ? 
Why  neutralized  with  NH4OH  ?) 

Confirmatory  Tests. 

For  Barium.  —  Sulphuric  acid  or  sulphates  precipitate  from 
soluble  barium  salts,  all  barium  as  BaSO4,  insoluble  in  water,  in 
dilute  acid,  and  in  alcohol.  Ammonium  oxalate  precipitates 
white  barium  oxalate,  soluble  in  acids.  Ammonium  hydroxide 
reprecipitates  it  from  the  acid  solution. 

If  Ba  is  in  mixture  with  Sr  or  Ca,  the  filtrate  from  the  precipitate  by 
K2Cr007  must  be  examined  for  the  latter  metals,  first  making  sure  that  the 
Ba  is  all  removed. 

Ba  salts  are  precipitated  by  soluble  phosphates,  as 
BaHPO4,  if  the  reagent  is  two  thirds  metallic,  and  Ba3(PO4)2 
if  the  reagent  is  full  metallic.  Potassium  chromate  or  dichro- 
mate  precipitates  BaCrO4,  yellow,  but  slightly  soluble  in  acetic 
acid,  soluble  in  HC1. 

For  Calcium.  —  Ammonium  or  potassium  oxalate  precipi- 
tates calcium  oxalate,  CaC2O4,  from  dilute  solutions  of  calcium 
salts,  not  soluble  in  acetic  but  soluble  in  hydrochloric  and 
nitric  acids.  If  a  platinum  wire,  which  has  previously  been 
dipped  into  hydrochloric  acid,  is  moistened  with  a  calcium 
salt  and  held  in  the  flame,  a  yellowish  red  color  will  be 
produced. 

For  Sironiium.  —  Precipitation  of  Sr  salts  by  sulphuric  acid 
or  sulphate  does  not  constitute  a  test  for  this  metal  if  Ba  is 
present  with  it.  A  mixture  of  Ba  and  Sr  salts  may  be  precipi- 
tated as  carbonates,  dissolved  as  chlorides,  the  solution  evapo- 
rated to  dryness  and  the  SrCl2  dissolved  out  by  absolute 
alcohol.  Potassium  chromate  precipitates  SrCrO4,  yellow,  sol- 
uble in  acetic  acid  (distinction  from  Ba).  Bichromates  (as 
K2Cr2O7)  do  not  precipitate  strontium  from  the  acetate  solution 
(distinction  from  Ba). 


62  QUALITATIVE    ANALYSIS. 

Strontium  compounds  color  the  flame  crimson. 

For  Magnesium.  —  The  precipitation  of  Mg  salts  with 
NH4OH  and  (NH4)2CO3,  and  the  solubility  of  the  resulting 
hydroxide  and  carbonate  in  NH4C1,  together  with  the  forma- 
tion of  the  phosphate  insoluble  in  NH4C1,  afford  distinctive 
tests  for  this  metal. 

Take  the  atomic  weights  of  calcium  and  barium  and  find 
their  mean.  What  is  it  ?  Can  you  find  other  facts  by  which 
it  may  be  seen  that  strontium  occupies  a  position  midway 
between  calcium  and  barium  ? 

Synoptical  View  of  the  Separation  of  Fourth  Group  Metals* 

Make  this  on  the  basis  of  the  preceding  work.  For  the 
method  of  doing  this  see  page  40  and  note  on  page  56. 


CHAPTER   XIV. 

OCCURRENCE  IN  NATURE  AND  USES  OF  FOURTH  GROUP 

METALS. 

How  in  nature  is  Ba  found  ? 

Character  and  uses  of  its  compounds  ? 

Is  metallic  Ca  found  in  nature  ? 

What  is  limestone  ?     Marble?     Chalk? 

What  is  the  composition  of  egg  shells,  clam  shells,  and 
corals?  Of  bones  ? 

What  is  quicklime?     From  what  is  it  prepared  and  how? 

What  is  slacked  lime  ?  Mortar  ?  "  Putty  coat "  or  "  hard 
finish  "  ?  (Ask  some  practical  mason.) 

What  is  water  lime  ?     Lime  water  ? 

What  is  bleaching  powder  ?     How  is  it  used  ? 

What  is  gypsum  ?     Plaster  of  Paris  ?     Land  plaster  ? 

Drive  out  the  water  of  crystallization  from  a  small  amount 
of  gypsum  by  carefully  heating  it  in  a  porcelain  evaporating 
dish.  Powder  the  residue,  and  make  it  into  a  paste  with  water. 
Allow  it  to  stand,  and  explain  the  results. 

What  is  the  most  frequent  ingredient  of  "hard"  water? 
When  will  boiling  make  hard  water  soft  ? 

What  is  the  reaction  between  hard  water  and  soap  ? 

Cases  of  chemical  action  are  constantly  occurring  in  every- 
day life,  and  it  should  be  the  habit  of  the  student  of  chemistry 
to  recognize  these,  and  be  able  to  explain  them.  An  illustra- 
tion of  this  thought  is  found  in  the  difficulty  experienced 
when  we  attempt  to  wash  with  soap  and  hard  water.  Soap  is 

63 


64  QUALITATIVE    ANALYSIS. 

a  salt  of  potassium  or  sodium,  and  easily  soluble  in  water. 
When,  however,  the  water  contains  calcium  carbonate  or  sul- 
phate a  reaction  takes  place  and  an  insoluble  calcium  stearate 
occurs,  thus,  — 

Sodium  stearate  -f-calcium  carbonate = calcium  stearate -|- 
sodium  carbonate. 

Tell  the  story  of  the  stalactite. 

What  is  fluor  spar  ?     Iceland  spar  ? 

Occurrence  of  Sr  ?     Compounds  and  uses  ? 

Prepare  carefully  a  small  amount  of  one  or  two  forms  of 
colored  fires  for  tableaux  and  pyrotechnics.  For  red  fire,  mix 
equal  parts  of  finely  powdered  Sr(NO3)2  and  KC1O3  with 
an  equal  bulk  of  pulverized  shellac.  Powder  each  substance 
separately  and  mix  carefully.  For  a  green  fire  use  Ba(NO3)2 
in  place  of  the  strontium  nitrate. 

Occurrence  of  Mg  ? 

Properties  and  uses  of  the  metal  ?  Hold  a  piece  of  Mg 
ribbon  in  the  forceps  and  heat  it  in  the  flame. 

What  is  magnesia  ?     Epsom  salts  ?     Magnesite  ? 

What  is  meerschaum  ? 


CHAPTER    XV. 
SEPARATION  OF  THE  METALS  OF  FIFTH  GROUP. 

What  metals  are  precipitated  by  (NH4)2CO3  ? 

What  metals  are  precipitated  by  KOH  or  NaOH  ? 

What  metals  remain  to  constitute  a  fifth  group  ? 

Of  these,  which  are  precipitated  by  H2C4H4O6  ? 

Which  by  H2C4H4O6  and  C2H5OH? 

Note  which  of  the  metals  of  the  Fifth  Group  impart  a 
characteristic  color  to  the  flame  when  a  Pt  wire  is  moistened 
in  a  salt  of  each  and  held  in  the  colorless  alcohol  or  Bunsen 
flame.  Study  these  flames  as  seen  through  blue  glass.  The 
best  result  will  be  obtained  if  the  wire  is  first  moistened  in 
HC1  and  then  in  the  salt  to  be  tested. 

Note  the  odor  given  off  when  KOH  is  mixed  with  an 
ammonium  salt  and  gently  warmed.  Test  the  gas  given  off 
with  a  moistened  red  litmus  paper. 

Note  the  easy  and  thorough  evaporation  of  ammonium 
compounds  when  a  drop  is  placed  on  the  platinum  foil  and 
gently  heated. 

For  contrast  to  this,  evaporate  in  the  same  way,  CaCl2,  or 
K2Cr2O7,  or  MnCl2. 

Rinse  a  beaker  glass  with  ammonia  and  a  second  one  with 
hydrochloric  acid,  keeping  them  separated  by  covering  each 
with  a  piece  of  paper.  Now  bring  the  mouths  of  the  beakers 
together  and  withdraw  the  papers.  Explain  the  result. 

The  metal  lithium,  Li,  occurs  in  nature  in  small  quanti- 
ties but  is  quite  widely  distributed,  being  found  in  the  ashes 
of  many  plants,  notably  in  that  of  tobacco  and  the  beet.  It  is 

65 


66  QUALITATIVE    ANALYSIS. 

the  lightest  of  the  metals;  it  melts  at  180°,  and  burns  with 
an  intense  white  light. 

Lithium  compounds  color  the  flame  a  beautiful  red. 

The  phosphate  and  carbonate  of  lithium  are  but  spar- 
ingly soluble  in  water  and  hence  may  be  precipitated  from 
concentrated  solutions  of  lithium  salts. 

From  the  above  study  of  these  metals  may  be  devised  a 
method  of  separation  of  the  metals  of  the  fifth  group. 


CHAPTER    XVI. 

OCCURRENCE  IN  NATURE  AND  USES  OF  FIFTH  GROUP 

METALS, 

Drop  a  bit  of  metallic  Na  or  K  into  a  dish  of  water  and 
ask  yourself  whether  these  metals  could  possibly  exist  in  a 
free  state. 

What  is  rock  salt  ?  What  is  common  salt  ?  Where  found 
and  how  prepared  for  use  ?  What  other  compounds  are  asso- 
ciated with  salt  in  sea  water  ? 

Moisten  some  wood  ashes  with  HC1  and  examine  the  flame. 
Dissolve  wood  ashes  in  water,  filter  and  concentrate  the  solu- 
tion, and  treat  with  tartaric  acid.  Treat  the  concentrated  solu- 
tion with  HC1  and  test  the  gas  given  off. 

Describe  and  explain  the  chemistry  of  the  old-fashioned 
"leach  tub." 

What  is  lye  ?     Hard  soap  ?     Soft  soap  ?     How  made  ? 

Burn  some  hard  soap  to  an  ash,  moisten  with  HC1,  and 
study  the  flame  reaction. 

What  is  gunpowder  ?     Dynamite  ? 

Take  a  piece  of  ordinary  phosphorus  as  large  as  a  pin's 
head,  and  sufficient  finely  pulverized  potassium  chlorate  to 
cover  it.  Fold  the  mixture  closely  in  a  piece  of  writing  paper, 
place  upon  an  anvil,  and  strike  it  a  sharp  blow  with  a  hammer. 
Use  small  quantities. 

Rub  together  in  a  mortar  small  quantities  of  potassium 
chlorate  and  flowers  of  sulphur,  keeping  the  hand  protected 
with  a  glove,  and  holding  the  mouth  of  the  mortar  away  from 
the  face. 

Fill  a  small  Erlenmeyer  flask  with  water  and  place  in  the 


68  QUALITATIVE    ANALYSIS. 

bottom  some  very  small  pieces  of  phosphorus  and  a  few 
crystals  of  potassium  chlorate.  With  a  thistle  tube  direct  a 
few  drops  of  strong  H2SO4  upon  the  chlorate.  Presently  the 
phosphorus  takes  fire,  and  burns  brightly  under  the  water. 

What  is  saltpetre  ?     Glauber's  salt  ? 

What  is  saleratus  ?  How  made  ?  Soda  ?  Sal  ammoniac  ? 
Saliva  ? 

What  is  borax?  Why  used  by  the  blacksmith  ?  Why  by 
the  barber  ?  Does  borax  soften  hard  water  ?  Try  it. 

What  is  caustic  soda  ?     Caustic  potash  ? 

Pulverize  a  little  window  glass,  moisten  with  HC1  and 
test  for  flame  reaction.  Do  the  same  with  a  broken  test  tube 
and  see  if  there  is  a  difference  between  the  two. 

What  is  common  alum  ? 

How  is  oxygen  obtained  from  potassium  chlorate  ? 

From  what  is  "laughing  gas"  obtained? 


CHAPTER  XVII. 
PERIODIC   LAW   OF   THE   ELEMENTS. 

The  famous  generalization,  known  as  the  periodic  law  of 
the  elements,  possesses  great  interest  after  the  student  has 
passed  over  the  work  of  grouping  and  separating  the  metals. 
A  preliminary  study  of  the  subject  may  be  made,  as  suggested 
below,  but  the  fuller  treatment  must  be  looked  for  in  larger 
works. 

1.  Arrange    the    elements    in    the    order   of    their   atomic 
weights  from  the  one  having  the  least   to  the  one  having  the 
greatest. 

2.  Ignoring  H  (why  ?)  and  beginning  with  the  next  in  the 
scale,   rearrange  the  elements,  as  they  appear  in   (i),  in  hori- 
zontal series. 

(a)  In  the  first  series  place  the  first  seven  elements. 

(b)  In  the  second  series,  the  next  seven  elements,  placing 
the  eighth  under  the  first,  the  ninth  under  the  second,  etc. 

(c)  In  the  third  series  put  ten  elements,  placing  the  fif- 
teenth under  the  eighth,  the  sixteenth  under  the  ninth,  and  so 
on. 

(d)  In  the  fourth  series  put  six  elements,  the  twenty-fifth 
under  the  fifteenth,  and  so   on,  but   leaving  the  twenty-eighth 
blank. 

(e)  In  the  fifth  series  put  ten  elements,  the  thirty-second 
under  the  twenty-fifth  and  leaving  the  thirty-eighth  blank. 

(f)  The  sixth  series  consists  of  the  seven  elements  begin- 
ning with  Ag. 

(g)  In  the  seventh   series  will  occur,  as  the  first  three 
elements,  Cs,  Ba,  La. 

69 


/O  QUALITATIVE    ANALYSIS. 

3.  Now  notice  that  the  valency  of  the  elements  of  the  first 
series  begins  with  one,  increases  to  a  maximum  and  decreases 
to  one.     Is  this  generally  true  of  all  the  series  ? 

4.  Adapt  the  proper  specific  gravities  to  the  second  series 
and  notice  whether  a  law  similar  to  that   in  (3)   can  be  ob- 
served.    Is  this  true  of  other  series  ? 

5.  What  group  of  metals  is  found  in  the  first  vertical  col- 
umn ?     What  in  the  second  ?     What  group  of    non-metals  is 
found  in  the  seventh  vertical  column  ? 

6.  Could  the  atomic  weight,  valency,  and  specific  gravity  of 
the  element  which  will  (when  found)  fill  the  blank  place  in  the 
fourth  series  be  approximately  determined  ? 

These  and  many  other  facts  are  summed  up  in  the  state- 
ment that  the  properties  of  the  elements  and  their  compounds 
present  themselves  as  periodic  functions  of  the  atomic  weights. 

Consult  Encyclopaedia  Britannica,  Vol.  V,  p.  543  ;  Smith's 
Richter's  Inorganic  Chemistry,  p.  241  ;  Roscoe  and  Schorlem- 
mer's  Treatise  on  Chemistry,  Vol.  II,  Pt.  II,  p.  506 ;  or  any 
late  work  on  general  chemistry. 


CHAPTER    XVIII. 

UNKNOWNS. 

In  order  to  insure  clearness  in  the  practical  use  of  the 
methods  for  the  identification  and  separation  of  metals  which 
have  been  formulated  from  the  preceding  work,  a  few  sugges- 
tions will  here  be  given  in  the  way  of  recapitulation  of  those 
methods. 

1.  If  the  substance,   the  composition  of  which  it  is  desired 
to  know,  is  in  the  solid  state,  it  is  dissolved  by  some  of  the 
methods  given  in  Chapter  IV. 

2.  A  small  portion  of  the  solution  is  treated  with  HC1,  and, 
in  case  a  precipitate  results,  enough  of  the  solution  is  used  to 
precipitate  a  sufficient  quantity  for  the  work  of  separation  in 
first  group. 

Enough  HC1  must  be  used  to  completely  precipitate  the  first  group  metals, 
if  it  is  suspected  that  other  groups  are  present.     Why  ? 

The  precipitate  is  filtered,  washed  (why  ?)  and  treated  with 
hot  water  and  NH4OH.  See  Chapter  VII. 

3.  The  filtrate  from  Group  I  (if  first  group  be  present),  or 
the  original  substance,  is  treated  with  HC1+H2S.     A  precipi- 
tate shows  the  presence  of  second  group  metals,  and  these  will 
be  examined  according  to  Chapter  IX. 

4.  The  filtrate  from  Group  II,  freed  from  HC1  and  H2S  by 
boiling  (if  Group  II  be  present),  or  (if  Group  I  or  II   be  not 
present)  the  original  sohition,  is  now  treated  with   HNO3  (to 
oxidize  ferrosum),  NH4C1  (why?),  and  NH4OH.     A  precipitate 
indicates  the  presence  of  Fe,  Cr,  or  Al.     These  will  be  exam- 
ined by  the  methods  in  Chapter  XL 

5.  The  filtrate  from  (4),  or,  if  Fe,  Cr,  or  Al  be  not  present, 

71 


72  QUALITATIVE    ANALYSIS. 

the  solution,  already  treated  with  NH4C1  and  NH4OH,  is 
tested  with  (NH4)2S,  a  resulting  precipitate  indicating  that  the 
solution  contains  Mn,  Zn,  Co,  or  Ni.  These  will  be  separated 
by  the  methods  in  Chapter  XI. 

6.  If  metals  of  any  of  the  preceding  groups   be  present,  the 
filtrate  must  be  used  for  work  in  the  following  groups.     The 
filtrate  from  Group  III,  or  the  original  substance,  is  now  tested 
with  NH4C1  (why  ?),  NH4OH  (why?),  and  (NH4)2CO3.     The 
precipitate  is  washed  on  the  filter,  dissolved  with  acetic  acid, 
and  examined  for  Ba,  Ca,  and  Sr.     Chapter  XIII. 

7.  The    original    substance    is    examined   for    Fifth    Group 
metals,  precipitation  by  H2C4H4O6  for  NH4  and  K  ;  the   odor 
test  for  NH3,  and  the  flame   test  for  K,  Na,  and   Li.     Chapter 
XV. 

8.  The  metal  having  been  found,  the  acid  is  next  looked  for 
by  methods  in  Chapter  XIX. 

Mixtures. 

The  analysis  must  be  guarded  at  certain  points  when  a 
mixture  of  several  substances  is  to  be  examined.  In  the  first 
place,  there  must  be  complete  precipitation  and  separation  of  the 
metals  of  one  group,  or  one  division  of  a  group,  before  the 
filtrate  can  be  examined  for  other  metals.  This  arises  from 
the  fact  that  the  salt  of  any  metal  will  precipitate  with  the  re- 
agents of  all  the  groups  succeeding  the  one  in  which  it  belongs, 
and  hence  false  indications  will  be  gained  unless  complete  sepa- 
ration of  one  metal  is  made  before  search  is  made  for  another. 

Again,  complications  will  arise  if  mixtures  of  dry  salts  are 
to  be  examined.  The  chief  difficulty  in  such  cases  will  arise 
in  getting  the  substance  into  solution.  A  little  thoughtfulness 
will  enable  the  student  to  guard  against  any  possible  cases. 
For  example,  the  substance  may  be  a  mixture  of 

(a)  Two  salts,  both  of  which  are  soluble  in  water  and 
such  as  will  not  react  on  each  other  when  dissolved.  Ferrous 
sulphate  and  manganous  chloride. 


UNKNOWNS.  73 

(b)  Two   salts,    both    of    which    are    soluble    in    water   but 
which  will  react  on  each  other  as   soon  as  dissolved,  forming 
one   salt    that    is    insoluble.       Lead     acetate    and    manganese 
chloride. 

(c)  Two  salts,  one  soluble  in  water  and  the  other  insolu- 
ble.    Calcium  carbonate  and  potassium  nitrate. 

(d)  Two   salts,    both    insoluble    in    water,    both    soluble   in 
HC1  ;  or,  one  soluble  in  HC1,  the  other  not,  etc. 

It  will  be  profitable  for  the  student  to  extend  this  list  of 
possible  cases. 


CHAPTER    XIX. 


ACIDS. 

The  work  thus  far  has  had  for  its  end  the  detection  and 
recognition  of  the  metals.  It  has  been  no  part  of  the  work  to 
inquire  what  acids  have  been  combined  with  these  metals  only 
so  far  as  the  known  composition  of  the  reagents  used  have 
made  these  apparent. 

The  Grouping  of  the  Acids. 

As  in  the  metals,  the  acids  may  be  thrown  into  provisional 
groups  according  to  their  behavior  with  certain  reagents. 

The  following  scheme  suggests  a  classification  of  the  acids, 
the  reagents  to  be  used,  and  the  order  in  which  the  steps  are 
to  be  taken  :  — 

GROUP  I  —  Group  reagent,  BaN03,  causing  precipitation  from  neutral  solu- 
tions of  the  salts  of 


H,Cr04 
H3As03 
H3As04 

GROUP  II  —  Group  reagent,  AgN03,  and  not  precipitated 
by  BaN03,  in  solutions  of  salts  of 

TTP1 

H2S04 
H3P04 
H3B03 

±11/1 

HBr 
HI 
HCN 

GROUP  III  —  Salts  of  acids  not  precip- 
itated by  BaN03  or  AgN03. 

H2C204 
HF 

H3FeC6N6 

HN03 
HNO.,* 

GROUP  IV  —  Organic 

HIO,, 

H4FeC6N6 

HC10, 

acids,  which  carbon- 

H2C03 

H2S 
HC10 

HBrO,* 

ize  on  heating. 

H2SiF6 
H2S03 
H4Si04 

HC102 
HCNS 

HC,H302 
HC104 
H,Mn04* 

HC2H302 
H2C4H406 

H2C4H40C 

*  May  precipitate  with  silver  nitrate  if  the  solution  is  concentrated. 

74 


ACIDS.  75 


Notes  and   Queries. 

For  a  brief  course  in  Qualitative  Analysis,  only  the  acids  given  on  the  list 
on  page  12  may  be  studied. 

The  salt  of  any  acid  will  give  the  test  of  that  acid. 

The  presence  of  one  acid  will  generally  not  interfere  with  the  detection  of 
others ;  so  that  the  different  acids  of  which  a  mixture  is  composed  may  be 
tested  for  in  separate  portions  of  the  original  substance. 

Metals  should  generally  be  determined  before  search  is  made  for  the  acids, 
as  the  work  for  the  former  often  gives  indication  of  the  presence  of  some 
special  acid  ;  or  the  evidence  may  make  it  possible  to  exclude  from  considera- 
tion one  or  more  groups  of  acids.  For  example,  if  the  substance  under 
examination  is  soluble  in  water  and  contains  Ba,  none  of  the  first  group  of 
acids  can  possibly  be  present.  Why? 

Which  of  the  acids  of  Group  I  contain  elements  which  would  be  detected 
in  the  examination  for  metals? 

Of  the  salts  of  barium  formed  by  the  first  group  of  acids,  BaS04  and 
BaSiF6  are  insoluble  in  HC1,  all  others  soluble. 

How  many  of  the  first  group  of  acids  will  precipitate  with  AgN03?  When 
will  this  fact  complicate  the  analysis? 


Further  Examination  of  Salts  for  Acids. 

The  work  suggested  in  the  table  and  the  pages  which  follow  should  be  done 
by  the  student  in  the  laboratory,  with  known  substances,  the  equations  should 
be  written  for  reactions,  and  the  results  recorded  in  the  permanent  note- 
book. 

Many  acids  are  separated  from  their  salts  by  H2SO4,  and 
when  thus  set  free  may  often  be  detected  by  their  character- 
istic odor  or  color.  Thus,  when  a  chloride,  as  NaCl,  is  treated 
with  H2SO4,  hydrochloric  acid  is  given  off  and  may  be  recog- 
nized by  its  sharp  and  penetrating  odor. 

2NaCl+H2S04=Na2S04+2HCl. 

The  Method.  —  Strong  sulphuric  acid  is  added  to  the  salt  to 
be  tested  (the  latter  in  the  solid  form,  or,  at  least,  in  a  concen- 
trated solution),  the  solution  gently  warmed,  and  the  following 
results  looked  for  : 


76 


QUALITATIVE    ANALYSIS. 


SALTS. 

ODOR. 

COLOR. 

REMARKS. 

Acetates, 

Vinegar, 

Colorless. 

Arsenates, 

No  escape  of  gas. 

Arsenites, 

No  escape  of  gas. 

Borates, 

No  escape  of  gas. 

Bromates, 

Odor  of  Cr, 

Brown. 

Bromides, 

Acrid, 

Brown. 

Carbonates, 

None, 

Colorless. 

Chlorates, 

Odor  of  Cl, 

Yellow. 

Detonates. 

Chlorides, 

Penetrating, 

Colorless. 

Chromates, 

None, 

Colorless. 

Cyanides, 

Peach  Blossom, 

Colorless. 

Ferro-cyanides, 

44                            44 

Colorless. 

Ferri-cyanides, 

4  4                            44 

Colorless. 

Fluorides,                  Poisonous, 

Colorless. 

Hypochlorites, 

Odor  of  Cl, 

Greenish. 

Hyposulphites, 

See  Thiosulphates. 

I  o  elates, 

No  escape  of  gas. 

Iodides, 

Irritating, 

Violet. 

Nitrates, 

Sometimes      ni- 

Colorless. 

trous  fumes. 

Nitrites, 

Irritating, 

Red. 

Oxalates, 

None, 

Colorless. 

Phosphates, 

No  escape  of  gas. 

Silicates, 

No  escape  of  gas. 

Sulphates, 

No  escape  of  gas. 

Sulphites, 

Burning  S, 

Colorless. 

Sulphides, 

Rotten  Eggs, 

Colorless. 

Tartrates, 

SO0,  CO0,  CO, 

Colorless. 

Thiosulphates, 

so;, 

Colorless. 

t 

Confirmatory  Tests. 

After  the  preliminary  tests  have  been  made  as  above,  any 
indication  there  obtained  may  be  confirmed  by  making  special 
tests  for  the  acids  as  follows  : 

For  Acetic  Acid,  HCZHZ0Z,  in  Acetates.  —  Sulphuric  acid,  ap- 
plied to  a  solid  or  concentrated  solution  of  an  acetate,  separates 
acetic  acid,  which  may  be  recognized  by  the  well-known  vinegar 
odor.  If  alcohol  be  added  to  the  same  solution,  •"  acetic  ether," 
or  ethyl  acetate,  C,H5C2H,O2,  will  be  formed  and  recognized  by 
its  fragrant  odor. 


ACIDS.  77 

Acetates  treated  with  FeCl3  give  a  red  solution  of  ferric 
acetate.  Compare  this  solution  with  the  blood-red  solution  of 
ferric  sulphocyanide. 

Arsenaies  and  Arsenites. — These  will  be  determined  in 
connection  with  the  work  in  the  second  group  of  metals. 

For  Boric  Acid  in  Borates. — The  element  boron,  B,  forms 
but  one  oxide,  boracic  anhydride,  B2O3,  and  the  corresponding 
acid  is  orthoboric  acid,  H3BO3.  By  heating  this  to  the  boiling 
temperature,  orthoboric  acid  is  converted  into  metaboric  acid, 
HBO2. 

The  common  commercial  salt  is  "  borax  "  or  sodium  bibo- 
rate,  Na2B4O7,  (NaBO2)2B2O3. 

The  common  test  for  a  borate  is  conducted  as  follows  :  If 
a  borate  is  moistened  with  H2SO4  in  an  evaporating  dish,  and 
alcohol  added,  on  igniting  the  latter  a  green  flame  is  produced. 
Copper  interferes  with  this  test,  and  if  present  should  be 
removed  by  H2S  and  the  test  for  a  borate  made  in  the  filtrate. 

For  Bromic  Acidf  HBrOz,  in  Bromaies.  —  All  the  bromates 
are  soluble  in  water,  except  Ag,  Pb,  and  (Hg)2"  which  are  spar- 
ingly soluble.  Silver  nitrate  precipitates,  from  concentrated 
solutions,  silver  bromate,  AgBrO3,  white,  soluble  in  NH4OH. 
Hydrochloric  acid  separates  bromine  from  this  precipitate 
which  will  color  carbon  disulphide  yellow.  Compare  AgBr. 

For  Hydrobromic  and  Hydriodic  Acids,  HBr  and  HI,  in  Bromides 
and  Iodides.  —  Make  a  thin  paste  by  heating  a  small  portion  of 
starch  in  water  in  a  test  tube.  Add  the  solution  to  be  tested. 
Now  add  to  the  mixture,  drop  by  drop,  chlorine  water.  A 
yellow  color  will  be  produced  by  bromine,  and  an  indigo  bhie  by 
iodine. 

KI+C1=KC1+I. 

KBr+Cl=KCl+Br. 

The  chlorine  water  may  be  made  by  covering  a  minute  particle  of  KC103 
with  HC1  and  heating.  When  the  chlorine  fumes  are  liberated  freely,  dissolve 
them  in  water,  thus  forming  a  green  solution. 


78  QUALITATIVE   ANALYSIS. 

Carbon  disulphide,  CS2,  may  be  used  in  place  of  the  starch, 
in  which  case  the  iodine  gives  a  violet  red  color,  and  the  bromine 
a  yellow  or  reddish  yellow. 

For  Carbon  Dioxide,  £02,  in  Carbonates.  —  Treat  a  carbonate 
with  H2SO4  in  a  test  tube  and  quickly  bring  the  mouth  of  the 
tube  to  that  of  another  containing  Ca(OH)2  solution,  allowing 
the  CO2  to  pass  from  the  first  tube  into  the  second,  finally  shak- 
ing the  latter  so  as  to  mingle  the  gas  with  the  lime  solution. 
A  white  precipitate  of  CaCO3  will  be  formed. 

With  a  piece  of  glass  tubing,  pass  air  from  the  lungs  into 
clear  lime  water  and  note  the  result.  What  is  "  choke  damp  "  ? 

For  Chloric  Acid,  HCIOZ,  in  Chlorates.  —  The  greenish  yel- 
low gas  and  the  detonation,  caused  by  treating  a  chlorate  with 
H2SO4  and  warming,  are  sufficient  for  the  determination  of 
this  acid. 

Use  small  quantities  of  the  chlorate  and  keep  the  test  tube  pointed  away 
from  the  face. 

Take  a  small  quantity  of  dry  KC1O3,  divide  in  two  por- 
tions. Dissolve  one  in  water  and  add  AgNO3.  Heat  the 
other  to  redness  in  a  test  tube  or  crucible,  dissolve  the  residue 
in  water  and  add  AgNO3.  Explain  the  difference  of  the  two 
results. 

For  Hydrochloric  Add,  HCI,  in  Chlorides.  —  Only  the  chlo- 
rides of  the  first  group  of  metals  are  insoluble  in  water.  This 
statement  is  only  true  for  normal  chlorides  as  some  basic  chlo- 
rides are  insoluble  in  water.  Consult  some  larger  work. 

Hydrochloric  acid  is  a  gas  at  ordinary  temperatures,  and, 
if  a  glass  rod  wet  with  AgNO8  be  held  at  the  mouth  of  a  test 
tube  in  which  a  chloride  has  been  treated  with  H2SO4,  a  ivhite 
precipitate  of  AgCl  will  be  formed  on  the  rod.  This  precipitate 
will  readily  dissolve  in  NH4OH  and  reprecipitate  by  acidulating 
with  HNO3. 

Any  soluble  chloride  added  to  a  solution  of  a  lead  salt  will 
precipitate  lead  chloride,  soluble  in  hot  water. 


ACIDS.  79 

Any  chloride  with  H2SO4  and  MnO2  will  give  Cl. 

For  Chromic  Acid,  H2Cr04,  in  Chromates.  —  Lead  salts  pre- 
cipitate, from  solutions  of  chromates,  lead  chromate,  PbCrO4, 
"chrome  yellow''  Barium  salts  precipitate  barium  chromate, 
BaCrO4,  yellowish  white.  Silver  salts  yield  a  dark  red  silver 
chromate,  Ag2CrO4.  Mercurous  nitrate  precipitates  mercurous 
chromate,  Hg2CrO4,  orange  red. 

For  Hydrocyanic  Acid,  HCN,  in  Cyanides.  —  Hydrocyanic  acid 
having  been  set  free  by  H2SO4  will  precipitate  AgCN  from 
silver  nitrate  on  a  glass  rod.  The  silver  cyanide  possesses  the 
same  solubilities  as  silver  chloride,  and  hence  arises  the  neces- 
sity for  some  additional  test  to  distinguish  between  them,  viz., 

A  cyanide  may  be  changed  to  a  sulphocyanide  as  follows  :  To 
a  portion  of  the  material,  supposed  to  be  a  cyanide,  in  an  evap- 
orating dish,  add  a  few  drops  of  (NH4)2S  and  warm  until  the 
excess  of  sulphide  is  all  driven  off.  Add  HC1  to  acid  reaction 
and  test  the  solution  with  FeCl3.  A  blood  red  solution  indi- 
cates that  the  original  substance  was  a  cyanide.  The  red  solu- 
tion should  decolor  with  HgCl2. 

For  Ferro-  and  Ferricyanides. 


REAGENTS    ADDED   TO 

FERROCYAN1DES 

FERRICYANIDES 

Bismuth  salts 
Copper  salts 
Ferrous  salts 
Ferric  salts 
Silver  salts 

Greenish  white  pre. 
Red  brown  pre. 
Whitish  blue  pre. 
Prussian  blue  pre. 
White  pre. 

Light  brown  pre. 
Olive  green  pre. 
Blue  pre. 
Green  solution. 
Red  brown  pre. 

For  Hydrofluoric  Acid,  HF,  in  Fluorides.  —  Mix  the  solid  fluor- 
ide with  solid  acid  potassium  sulphate,  KHSO4.  Dip  in  the 
mixture  a  borax  bead  formed  on  a  platinum  wire  and  test  in  the 
Bunsen  or  alcohol  flame.  A  green  flame  appearing  only  for  an 
instant  indicates  the  formation  of  BF3.  Confirm  by  the  "  etch- 
ing "  test  :  The  glass  which  is  to  be  etched  is  covered  with  a 
thin  coating  of  wax  and  through  this  the  design  is  drawn.  The 
glass  is  now  placed  over  a  leaden  dish  in  which  calcium  fluoride, 


8O  QUALITATIVE    ANALYSIS. 

CaF2,  has  been  placed.  The  mixture  is  gently  warmed,  until 
chemical  action  commences,  and  then  is  to  be  left  for  several 
hours. 

CaF2+H2S04=2HF+CaS04. 

For  lodic  Acid,  HIOZ,  in  lodaies.  —  Consult   some  larger  work. 

For  Nitric  Acid,  HNOZ,  in  Nitrates.  —  All  normal  nitrates 
are  soluble  in  water.  The  "brown  ring"  test  is  as  follows: 
Take  in  a  test  tube  a  small  quantity  of  H2SO4;  incline  the  test 
tube  and  pour  an  equal  amount  of  ferrous  sulphate  in  such  a 
way  that  the  two  liquids  do  not  mix.  Cool,  and  drop  into  the 
mixture  the  substance  to  be  tested.  If  a  nitrate  is  present,  the 
FeSO4  reduces  the  HNO3  to  NO,  and  this,  dissolving  in  the 
excess  of  FeSO4,  forms  a  ring  of  dark  brown  liquid  in  the  layer 
between  the  two  liquids. 

The  formula  for  the  brown  ring  is  (FeSO4)2NO  ;  let  the 
student  write  the  equations  for  the  successive  steps  of  the  pro- 
cess and  finally  the  equation  for  the  complete  test.  As  prepara- 
tory to  this,  notice  that  free  nitric  acid,  HNO3,  gives  the  brown 
ring  without  the  aid  of  the  H2SO4.  Then  why  is  the  H2SO4 
used  ?  What  is  the  initial  movement  ?  When  does  it  take 
place  ?  The  ferrous  sulphate  has  been  oxidized  to  ferric  sul- 
phate. How  many  molecules  of  ferrous  sulphate  are  needed 
for  one  molecule  of  ferric  sulphate  ?  What  else  is  needed  ? 
From  what  source  is  this  derived  ?  What  has  been  the  change 
produced  in  the  H2SO4  ?  By  what  was  this  change  produced  ?• 
How  much  O  has  been  liberated  ?  How  much  H2SO4  can  this 
decompose  ?  How  much  FeSO4  can  this  oxidize  ?  etc. 

How  will  an  iodide  behave  when  examined  by  this  test  ? 

For  Nitrous  Acid,  HNOV  in  Nitrites.  —  The  same  test  may 
be  made  as  for  nitrates,  with  the  difference  that  the  evolution 
of  the  nitrons  fumes  is  much  more  abundant.  Acetic  acid  may 
be  used  in  place  of  H2SO4  and  this  makes  a  distinction  between 
nitrates  and  nitrites. 


ACIDS.  8 1 

For  Sulphuric,  Oxalic,  and  Phosphoric  Acids,  in  Sulphates,  Oxalates 
and  Phosphates.  —  Using  the  potassium  salts  of  these  acids  as 
types,  the  method  of  testing  may  be  summarized  as  follows :  — 

K,SO.  1  fBaS04    1  fBaS04 

(BaCl2) 
K,C.,04  Kneutral)+<  >  =  ^  CaC204  UHCl=-{  CaCl2+H2C204. 

(CaCl0) 
K3P04  j  I  CaHP04  I  LCaCla+H8P04. 

CaCl2+H2C204}  (CaC204  }  (CaC204 

>  +NH4OH=  <  ?  +HC2H302  <  ~ 

CaCl2+H3P04  )  (CaHP04)  (CaH4(P04)2 

Test  the  solution  of  the  phosphate  with  ammonium  mo- 
lybdate,  (NH4)2MoO4.  A  yellow  precipitate,  after  warming,  is 
indication  of  a  phosphate. 

For  Silicic  Acid,  in  Silicates.  —  If  a  bead  formed  on  a  plat- 
inum wire  with  "  microcosmic  salt,"  NaN'H4HPO4,  be  dipped 
in  a  powdered  silicate  and  intensely  heated,  small  spicules  of 
silica  will  be  seen  floating  in  the  fused  bead.  This  test  may 
serve  for  the  detection  of  silicates. 

Only  potassium  and  sodium  silicates  are  soluble  in  water. 
Other  silicates  are  made  soluble  by  first  fusing  them  on  the 
platinum  foil  with  a  mixture  of  Na  and  K  carbonates,  or  by 
boiling  in  a  solution  of  KOH  or  NaOH. 

For  Sulphurous  Acid,  H2S03,  in  Sulphites.  —  The  sulphites  of 
the  metals  of  the  alkalies  are  soluble  in  water,  all  others  in- 
soluble ;  hence,  solutions  of  sulphites  are  precipitated  by  the 
soluble  salts  of  all  metals  not  alkali.  Sulphurous  acid  and  sul- 
phites are  active  reducing  agents, 

0+H2S03=H2S04. 

Test  the  last  statement  by  reducing  ferric  salts  and  potas- 
sium permanganate. 

For  Hydrosulphuric  Acid,  H2S,  in  Sulphides.  —  Sulphides, 
treated  with  HC1  or  H2SO4,  evolve  H2S  which  may  be  recog- 
nized by  its  odor  and  by  blackening  paper  wet  with  lead  acetate. 


CHAPTER    XX. 
SOME  DRY  PROCESSES, 

The  work  thus  far  has  been  carried  on  by  processes 
known  as  "the  wet  way."  Oftentimes  the  dry  solid  may  prof- 
itably be  examined  either  as  preliminary  to  the  regular  exam- 
ination or  as  confirmatory  to  the  results  there  reached. 

Flame  Tests. 

A  platinum  wire  is  moistened  in  HC1  and  dipped  into  the 
solid,  or  concentrated  solution,  and  held  in  the  flame.  Char- 
acteristic colors  are  imparted  to  the  flame  :  — 

Yellow  indicates  Na  (obscured  by  blue  glass). 

Violet  indicates  K  (obscured  by  the  yellow  of  Na,  if  that 
metal  is  present). 

Crimson  indicates  Sr. 

Red  indicates  Ca,  Li. 

Greenish  white  indicates  Zn. 

Green  indicates  HC1,  H3BO3,  Ba  salts,  Cu  salts  (except 
the  chloride). 

Blue  indicates  CuCl2,  Pb,  As,  Sb. 

On  Charcoal. 

The  powdered  substance  is  placed  on  charcoal,  either  by 
itself  or  mixed  with  Na2CO3,  and  heated  with  the  blow  pipe, 
reducing  flame.  Characteristic  coatings  are  given  to  the  char- 
coal : 

White  and  volatile,  Sb  or  As.  (The  latter  gives  a  garlic 
odor.) 

Yellow  while  hot,  white  when  cold,  Sn,  Zn. 

Yellow  while  hot,  yellow  when  cold,  Pb,  Bi. 

Brown,  Cd. 

82 


SOME    DRY    PROCESSES.  83 

The  following  metals  yield  metallic  globules  when  heated 
on  charcoal  with  Na2CO3  : 

Malleable  beads,  Au,  Cu,  Ag,  Pb,  Sn. 

Brittle  beads,  Sb,  Bi. 

Magnetic  particles,  Fe,  Co,   Ni. 

Borax  Bead. 

A  clear  bead  is  obtained  by  fusing  borax  on  a  loop  of 
platinum  wire  ;  a  very  little  of  the  solid  substance  to  be  exam- 
ined is  placed  upon  it,  and  the  whole  fused  thoroughly  in  the 
oxidizing  flame. 

Colored  beads  are  obtained  which,  when  cold,  are  as  fol- 
lows : 

Blue,  Co  or  Cu  (the  latter  red  in  R.  F.). 

Green,  Cr;  light  yellow,  Bi. 

Light  yellow  (in  R.  F.  green),  Fe. 

Reddish  brown  (in  R.  F.  gray),  Ni. 

Amethyst  red  (in  R.  F.  colorless),  Mn. 

Care  of  Platinum  Vessels. 

"  Platinum  vessels  are  sometimes  considered  indestructible, 
but  they  are  not  so,  in  fact,  they  are  very  delicate  and  need  to 
be  handled  with  care. 

The  life  of  a  Platinum  crucible  depends  upon  whether  it 
be  of  pure  Platinum,  and  upon  the  treatment  it  receives  ;  there- 
fore, always  observe  the  following  rules  : 

1.  Keep  it  in  shape ;  do  not  bend  it;  provide  proper  recep- 
tacle (wood  block  or  plaster  cast,  with  a  wooden  plug  for  the 
inside,  fitting  the  crucible  exactly). 

2.  Keep  it  always  perfectly  bright  and  clean,  which  can  best 
be  done  by  means    of   fine  (round,  not    sharp)    sea   sand,    by 
moistening  the  finger,  dipping  it  into  the  sand,  and  rubbing  the 
crucible  till  bright.     Sometimes  HC1  will  remove  stains  quickly, 
but  in  other  cases  fusions  with  Na2CO3,  borax,  or  KHSO4  are 


84  QUALITATIVE    ANALYSIS. 

required  for  cleansing,  and  to  avoid  too  much  rubbing.     Clean 
it  after  each  and  every  use. 

3.  Apply  heat  with  care  ;  do  not  heat  too  quickly  or  cracking, 
due  to  sudden  expansion,  will  occur.     Do  not  cool  too  quickly  ;  a 
cold  blast  turned  on  when  the  metal  is  at  a  white  heat  will 
cause  the  metal  to  crack. 

4.  Apply  the  outer  oxidizing  flame ;    do  not  have  the  inner 
(reducing)  flame  touch  it,  or  a  gray  film  will  form  (showing  ir- 
regular surface  under  the  magnifying  glass). 

5.  Always  use  a  bright  platinum,  or  pipe  stem,  triangle  to  rest 
the  crucible  on. 

6.  Test  unknown  material  before  fusing  in  the  crucible.     If  no 
time  for  analysis  is  given,  heat  a  sample  of  the  material  between 
a  piece  of  folded  up  platinum  foil  and  note  the  action. 

7.  Never  fuse  nor  heat  in  it  the  following  :  free  metals  ;  easily 
reduced  metallic  oxides ;  the  salts  of  the  heavy  metals  (such 
as  lead,  tin,  bismuth,  antimony,  etc.),  especially  their  organic 
compounds. 

8.  Phosphoric  acids  in  some  phosphates,  in.  presence  of  organic 
substances,  render  the   platinum  very  brittle   at    high  temper- 
atures. 

9.  Other    substances    injurious    to    platinum,    under    certain 
conditions,  are  substances  evolving  free  chlorine,  sodium   and 
potassium  nitrates,  some  cyanides  and  sulphides  of  metals. 

10.  Contact   with  burning  charcoal  and   highly  carburetted 
flames  should  be  avoided." 


INDEX. 


ACETIC  ACID,  74,  76. 
Acids,  classification  of,  12,  74. 

list  of,  12. 

tests  for,  74,  81. 
Acid  radical,  12. 
Aluminum,  34,  35,  57. 
Ammonium,  65. 

Antidote  for  arsenical  poisoning,  49. 
Antimony,  43,  45,  46. 
Apparatus,  19. 
Aqua  regia,  23. 

Arsenic,  43,  44,  45,  49,  74,  7^,  77- 
Ashes,  67. 

Atomic  weights,  table  of,  9. 
BARIUM,  60,  61. 
Books,  reference,  21. 
Borax  bead,  83. 
Boric  acid,  74,  76,  77. 
Bromic  acid,  74,  76,  77. 
CALCIUM.  60,  61. 
Carbonic  acid,  74,  76,  78. 
Carbon  dioxide,  78. 
Charcoal,  tests  on,  82. 
Chemical  action,  8. 

affinity,  8. 

compound,  8. 
Chloric  acid,  74,  76,  78. 
Chlorine,  23. 
Chromic  acid,  74,  76,  79. 
Chromium,  54,  55. 
ELEMENTS,  table  of,  9. 

periodic  law  of,  69. 
Equation,  26,  27. 
Evaporation,  24. 
Exchangeable  hydrogen,  12. 
FLAME  TESTS,  82. 
Formulas,  how  named,  14. 
GLASS,  68. 
Gold,  50. 
Greek  fire,  64. 
HYDRACIDS,  12. 
Hydrobromic  acid,  74,  76,  77. 
Hydrochloric  acid,  74,  76,  78. 
Hydrocyanic  acid,  74,  76,  79. 
Hydriodic  acid,  74,  76,  77. 
Hydroferricyanic  acid,  74,  76,  79. 
Hydroferrocyanic  acid,  74,  76,  79 
Hydrofluoric  acid,  74,  76,  79. 
Hydrosulphuric  acid,  74,  76,  81. 
Ionic  ACID,  74,  76,  80. 
Iron,  53,  54,  55. 
LAKORATORY,  16. 
Laboratory  methods,  1-6. 


Lead,  38,  39. 
MAGNESIUM,  60-62. 
Manganese,  55. 
Marsh's  test,  44. 
Mercury,  38,  39,  48. 
Metal,  8. 

Metals,  grouping  of,  32. 
Method,  the  true,  2. 
Mixtures,  72. 
NEUTRALIZATION.  13. 
Nickel,  56. 

Nitric  acid,  53,  74,  76,  So. 
Nitro-hydrochloric  acid,  23. 
Nitrous  acid,  74,  76,  So. 
Nomenclature  of  acids,  12. 
of  salts,  13. 
Non-metal,  8. 
Note-book,  how  kept,  6,  30. 

OXACIDS,  12. 

Oxalic  acid,  74,  76,  81. 
Oxidation,  52,  53. 
PERIODIC  law  of  elements,  69. 
Phosphates,  56. 
Platinum  vessels,  84. 
Precipitation,  24. 
Program,  daily,  3. 
REAGENTS,  18. 

cost  of,  20. 
Reducing  agents,  53. 
SALTS,  classification  of,  13. 
Separation  of  first  group  metals,  38. 

of  second  group  metals,  43. 

of  third  group  metals,  51. 

of  fourth  group  metals,  59. 

of  fifth  group  metals,  65. 
Silicic  acid,  74,  76,  81. 
Silver,  38,  39. 
Soap,  63. 
Solubility,  22. 
Solubilities,  table  of,  31. 
Solution,  chemical,  23. 
physical,  22. 
physico-chemical,  24. 
Solvents,  23. 
Strontium,  60,  61. 
Student  in  laboratory,  4. 
Sulphuric  acid,  74,  76,  81. 
Sulphurous  acid,  74,  76,  81. 
TIME  required,  3. 
Tin,  43,  44.  45. 
Unknowns,  71. 
Valence  of  elements,  9. 
Zinc,  55. 


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